This feels like it's a decade too late. Yikes.
I personally gave up on Facebook about two years ago and deleted my account, but this announcement does remind me of the days where I used to plug a dozen different instant messaging clients into Adium back on my eMac G4. Those were the days.
Even iChat used to be able to manage quite a few messaging apps, including Gchat, AOL and a bunch of others if I recall. I really wish there was an open standard for messaging instead of everyone trying lock you into a silo. I guess the closest we have now is SMS, as insecure and crappy as it is?