Yahoo and Microsoft are knitting their networks more tightly together as they announce that Yahoo Messenger and Windows Live Messenger are now connected.

The new joint instant messaging community forms the world’s largest IM network with nearly 350 million user accounts.

Online contacts will now be viewed through the same contact list; once a user adds a Windows Live Messenger contact, they’ll show up on the Yahoo Messenger contact list; you can even send them a message when they’re logged off to be delivered when they come back online.

Yahoo conducted a study to determine that a third of IM users in the UK wanted to communicate using other IM networks. The research also showed that 77% of people believe that the ease of sending quick messages contributes to the growth in the use of IM, and 32% of respondents like using emoticons to express themselves while chatting.

Respondents were also rather randomly asked about what celebrities they’d like to chat to online; 34% said they’d like to talk with Sharon Osbourne, while only 19% wanted a word with Simon Cowell.