Facebook has a history to incorporating other sites' features. When Twitter got big, they created added "status". We should all do that with our companies.
Facebook had a status feature before Twitter was founded. They made it more prominent after Twitter became popular but I think that was just a coincidence.
Not just facebook... every other company in silicon valley is doing that. Even google's adwords was first invented by overture. Latest eg. Palm Pre (and 15 other smartphones) incorporating iPhone UI elements.
"Good artists copy, Great artists steal" - Pablo Picasso
In overture, you could buy the search results, though. Apparently, the founders looked at that and said "don't be evil."
you can do that in yahoo if you're in the know... yahoo owns the famous overture patent so that may be why.