The biggest difference between Twitter and Facebook updates (at the moment) is that your Facebook news feed is limited by who you have some connection to (albeit possibly very tenuous). The beauty (and ugliness) of Twitter is that it's interest or topic-based - you don't need a pre-existing connection to start following or viewing someone's public tweets.

That being said, I will be sad if Twitter is subsumed by Google or Facebook.

EDIT: Technically easy but Facebook is a good walled-garden (privacy controls). I don't know if they'll let some public weeds in just to compete with Twitter. Twitter allowing Facebook users to auto-post an update to their Twitter identity could work.