Twitter is so many things.
But at its core, its a functional checkin service isn't it?
If you use it the way most experts recommend, you are retweeting messages (links) from people you wanted shared, including a small mix of yours in for good measure.
Isn't that just telling people what you are reading? I've seen some automated Twitter tool discussion lately. The gist was that people didn't like referring something that they maybe hadn't read.
But that means that all functional checkins are just referrals right? Checking out an article, link, webpage, a restaurant, movie, book- it is all the same right?
So as long as Facebook and Twitter allow us to aggregate those "checkins" or referrals, we will keep doing it. And Twitter ain't going anywhere fast.