In what must be one of the most embarrassing Twitter sponsorship boobs, Oprah Winfrey (well, her account anyway) has posted a tweet declaring the US star's love for the Microsoft Surface tablet using the Twitter app on an iPad. How do we know? It was there on the tweet.

Or, at least, it was. The posting has now mysteriously changed to one that doesn't mention its source, but not in enough time to stop Uncle Tom Cobley and all noticing it first.

With close to 15 million followers, it's no surprise that Microsoft has punted a wodge of cash at one of America's top TV presenters in order to spread the word about its new tablet device. However, we suspect the Redmond software giant didn't quite expect the allegedly paid-for tweet to be overtly posted on the very device from which it is hoping to steal market share.

If this had happened in the UK, not only would it be majorly embarrassing - as it clearly is for the Oprah camp - but it could also warrant a rap on the knuckles from the Advertising Standards Authority. In Britain, the guidelines state that it must be made clear when a tweet is a promoted one. Wayne Rooney was charged by the ASA over a Nike-promoted tweet that was deemed to have been passed off as a personal one.

Pic: (cc) photo by Alan Light