Of course, it hasn't all been positive news for Facebook recently, but it is 15 years today since a fresh-faced, wide-eyed Mark Zuckerberg launched Facebook from his Harvard dorm on 4 February 2004. Little did Zuckerberg know that at just 19 years old he had changed the world - and the internet - forever.

Within four years, Facebook would overtake Myspace in the number of unique worldwide visitors. Within six years, Facebook would be the inspiration for a blockbuster film that won three Academy Awards and four Golden Globes.

Within eight years, Facebook would hold one of the biggest initial public offerings in Internet history and hit a peak market capitalization of over $104 billion. And within 10 years, Facebook would announce it had 1.228 billion monthly active users across the globe. It's now got 2.3 billion. 

Facebook is undoubtedly an enormous success. It's also starkly different than it was during Zuckerberg's brief Harvard days. It's added huge numbers of new features and interface adjustments, lifted registration limitations, launched some of the world's most successful mobile apps, acquired other hugely successful apps, and it's had major shakeups in its executive team.

So, how can one online service, which has experienced so many changes, still be so successful? Here are 10 of the key reasons. 

FacebookFacebook 3D photos How to create share and view 3D photos image 1

1. Facebook is easy to use

When people think of Facebook they also think of Twitter. They're rivals, right? Well, Facebook and Twitter are two entirely different beasts, but they both have something in common: social networking. Most people use them to socialise and network with friends, family, fans, businesses, and acquaintances. Unfortunately for Twitter, Facebook is just easier to use for most people. 

Facebook doesn't do any of that. Although it now recognises and supports @ for tagging and # for trending words, Facebook doesn't rely on them. For instance, on Facebook, you can start writing the name of a person in a status, and Facebook will understand what you're doing and allow you to tag that person. It's easy.

In fact, all of Facebook's features are easy. That's why your parents, aunts, uncles and grandparents can use it. You don't have to be a computer hacker like Zuckerberg to figure it out. And with such ease of use, millions upon millions of people have embraced Facebook and stuck with it for so long.

To use Twitter effectively, you have to understand @ symbols, hashtags and other such idiosyncrasies. These features are part of what make Twitter an ideal tool for seeing what's trending, sharing bits of information, finding news and so on. They're also what makes Twitter so confusing. 

Facebook10 reasons why facebook has thrived for 15 years image 1

2. Constant upgrades

Facebook loves to push out upgrades to its products. Some may argue that these upgrades cause the most uproar among users, but none of them to date have actually caused the social network to haemorrhage users.

Facebook's user interface has changed repeatedly over the years, for instance. It has added a news feed, timeline, cover photo, the list goes on. Facebook clearly wants to evolve, and not just on the web. The company's suite of mobile apps also receives extremely regular upgrades. That's because Facebook is more than willing to develop and test changes, even if users groan and complain about them via a million status updates.

3. Engaging features

Facebook is addictive. And that's because Facebook has some really engaging features. The website alone offers a news feed, messaging/chat, voice and video calls, the ability to like, follow, subscribe, Marketplace and more.

Apart from the UI and product tweaks, Facebook has also repeatedly rolled out new features. Some of them - such as Facebook's Messaging platform - have become very popular, while others - such as Facebook Beacon - have fizzled into nothing. But still, the company perseveres. 

FacebookFacebook has delayed unveiling its smart speaker due to recent data scandal image 1

4. Mobile movers

Facebook didn't waste any time moving to mobile. When numbers started suggesting a few years ago that people were using their smartphones and tablets more and more to access Facebook, the social network didn't skip a beat. It not only has the standard Facebook app for most platforms, it also has standalone apps for messaging, poking, uploading photos, reading news, and more.

5. Buying successfully

Facebook has acquired numerous companies - 77 in all. The key double though, are WhatsApp and Instagram. Facebook's record purchase is the $19 billion acquisition of Instagram, $2 billion purchase of Oculus and $1 billion buy of Instagram are probably the most notable. 

6. Worldwide users

You can't talk about Facebook's success without talking about its users, and they're worldwide. Facebook has around 2.3 billion users, approximately 85 per cent of whom are outside the US and Canada. Not only are they spread out across the globe, but they also range in age and sex.

 7. Forcing people to identify themselves

Facebook tries to eliminate anonymity on the web, which in turns makes it appear safe and more inviting to people from around the world. Former Facebook President Sean Parker once explained how Facebook began with colleges and forced college users to authenticate their email addresses. This limitation actually implemented a one person, one identity token practice that Facebook has roughly stuck with, though it now allows any user with a verified email to join.

FacebookFacebook Creator image 2

8. Facebook Connect

In 2008, Faceboook announced an extension of Facebook Platform called Facebook Connect. It made it easier for Facebook users to take their online identity with them across the web, according to Zuckerberg.

It also enabled them to share what they do online with their friends and stay updated on what friends doing, without having to create separate accounts for every website or app. They could simply use their Facebook login wherever Facebook Connect was available.

A small idea like Facebook Connect is an ideal example of how Facebook just gets it right. It also suggests that Facebook is forward-thinking. Because let's be real: a company with a vision for the future has a better chance of succeeding than one that doesn't (hello, again, Myspace).

9. Going public

When Facebook went public, many people thought it was absurd. Others however realised Facebook was cementing its place in history. Facebook didn't want to become a fad site; it wanted to be around in another century or two. To accomplish such a fantastical dream, Facebook had to make a switch to probability (beyond advertising).

To be honest, Facebook is also more powerful as a public company. Facebook's cash pile ballooned quite a bit after the IPO, giving it the resources to battle giants of the internet like Apple, Google, Amazon, Microsoft, all of which have heaping mounds of cash.

FacebookYouTube alternative Facebook Watch launches in the UK image 1

10. News feed video

Next year, Cisco believes that online videos will make up 80 percent of all consumer internet traffic. It's also been shown that the huge majoriyty of users (95 percent) retain information much more easily in a video compared to around 10 percent of users who retain it if it's written in text.

While YouTube was obviously at the forefront of the online video revolution, the growth of video on Facebook has been exponential over the last few years. According to Tublar Insights, over 500 million people watch video on Facebook every day, while the reach of a Facebook video hugely outweighs a photo. That's some staggering numbers.