I occasionally crosspost my status to Facebook from Twitter but I do it intentionally and selectively. I don't always crosspost but only when I'm posing a question or have a significant update.
I crosspost by using the #FB tag and by using the Facebook update button on Tweetdeck.
How about you?
Facebook/Twitter Clients 4 Answers
What is App.net 1 Answer
What is Google Buzz? 1 Answer