Why would it be bad? You won't be able to vote for your friend if you guys queue up together in a party, and the voting is done after the dungeon ends so that when someone threatens to "vote me mvp or i afk" you can just lie and say you'll vote for him, then leave as soon as the run is finished.

At least that's what I gathered from reading about the mvp system a few weeks back, I can't really remember too clearly.