Las week I found this picture in a Techcrunch post:
A weird traffic jam in Moscow city. It looks like something went wrong on the right lane and everybody was trying to reach de left one.
It remembers me a lot about what we do in social networks thesedays: Switching/jumping from one app to another depending on the "flow" of friends they´re already in. What little features (sometimes even invisibles) move users from one to another? In the Techcrunch post mentioned above it was the hidden "In reply to" option what moved users to use Friendfeed instead.