It's kind of tricky. I don't have a big problem with friends of mine who post their Farmville junk on their streams because it is dead simple to block those types of updates. Unfortunately, facebook doesn't offer a "filter this user's complaints about things you don't care about" so your options are to unfriend or block them from your stream. If you use Facebook mostly for the stream, if you block all stream posts, you might as well just remove them.