Loren Brichter invented the "pull to refresh" interface mechanism for Tweetie, a Twitter app he eventually sold to Twitter. Apparently he patented the idea sometime before the sale, so Twitter now owns the patent.
Paul Haddad of Tapbot says that Twitter won't enforce the patent but, gosh, where have we heard that before?
Update: A reader pointed out that this is not a patent...it's a patent application that hasn't even been reviewed yet. But it's clearly a novel invention and most likely will be accepted when reviewed. (thx, mike)