Smart piece from Om, though I think he maybe does not give enough weight to Twitter in this scenario. URI shorteners have been around for a long time, but have taken off only recently, and almost exclusively because of Twitter's 140-character limit. If Twitter, say, doubles that limit, or starts losing users to Facebook, etc. (where the limit is not really an issue), I suspect use of the shorteners will decline commensurately.
If I were an investor I'd probably think twice about throwing money at a service that is so predicated on the fickleness of users and the whims of app developers (e.g., TweetDeck, my favorite Twitter client, defaults to bit.ly for shortening, but that could change tomorrow), not to mention the sheer number of competing shortening services (TweetDeck alone supports 13 of them).
All of that said, I definitely do think there is serious value in being able to generate a list of the most currently-popular URIs from across the web (instead of just those that are bubbled up through a particular site, e.g., Digg).