It was going to happen sooner or later, but for me, Twitter is now dead. Facebook can now do everything that Twitter does, and more; not to mention that there are orders of magnitude more people on Facebook.
For those of us in Canada, Facebook just added Canadian cell carriers to their Mobile section. Bell Mobility, Aliant Mobility, Fido, and Rogers (Telus was curiously absent) are now able to be selected. Once you activate Facebook Mobile, you can post status updates to Facebook using your mobile phone, and you can specify which of your friends' status updates you want to receive as text messages. That's pretty much Twitter in a nutshell. The only things lacking are the IM integration, which was flaky at best anyway, and the third party app support, i.e., Twitterific.
Since Twitter couldn't manage to set up a Canadian short code, and I don't really feel like paying for international charges for using the UK number, I don't know how much I'm really going to be using Twitter anymore. You're on Facebook already anyway, right?