TechCrunch50 isn't really a competition, it's a series of product demos. This is kind of like presenting the philosophies of different religions and then voting on which one is the "best". The whole thing is subjective and there is absolutely no need to declare a winner, especially when the market will ultimately decide. This is exactly why YCombinator doesn't have investors vote on which company "won" Demo Day. I pity our american idol society that always wants a panel of judges to tell them what to like.

As for Yammer itself, I'm thoroughly unimpressed. At the least they could have made it look different than twitter. They even copied the UI. There were so many companies doing truly innovative things... TechCrunch50 seems like a total farce.