The General Manager of Reddit told me that he thinks Subreddits are successful, in part, because the service displays so many statistics (# of members, uniques, etc). As a result, redditors try their best to optimize them and the communities grow.
Similarly, we all try to optimize the number of Followers we have on Twitter. And the number of comments you had on your Myspace page was a BIG DEAL, way back when.
How important do you think it is for a social platform to give its users a number to optimize? Even pageviews on WordPress and LinkedIn are super addicting.
We purposefully left one-click interactions out of the Branch UX – "so that you're not influenced by popular opinion" – but I wonder if that's a mistake...