[Timothee]

That being said, the Google Buzz app is just using the same UI library that Google has developed for all their other mobile offers (Gmail, Calendar, GTalk, etc.).

I think you have two things:

1. Google developed their library of UI elements that looks a lot like the iPhone ones.

2. Using that library, they made a new interface for Buzz. It does look very similar to Brightkite's, but only the location part can be really argued as "inspired", the rest is pretty standard indeed.