Following someone on Twitter isn't too bad but Facebook friending someone is pretty intrusive and something that a lot of people don't usually do unless they know each other in real life or are pretty close in general. They should just have a regular friend system that doesn't require the use of external social networks.
Why is it dumb? It's a brand new social app, there's no established history yet. Once time has settled in and it's actually established a base of users then it would make sense to have a in app friend search feature. Including adding friends through the current widespread popular social apps is actually the smartest thing that they could have done. Many people that may not even be interested in games might try this app out simply because it's trending on Twitter or something.