it`s an element of interactive and it`s really nice way to involve users. You make followers think that their opinion is important for you and they also wont to know which variant will become "the winner of the game" =) But to get results of course you need a great numbers of followers=)
Creating viral posts like that on twitter (and instagram, tumblr, Facebook...) is my job haha. That is a "forced" viral post (extremely high exposure, at least 200k actual impressions if I had to guess) because the post itself lacks viral structure. Synergy between multiple accounts to fire up engagement right from the start (50% of those numbers are achieved in the 1st minute after posting) is crucial. This sort of thing is one of my specialties