Yeah, all this 'vote for your favourite day' competition etc fills me with dread too. Seems ridiculous to do if you've still got a third of the acts to announce. Unless, of course, the acts they have ready to announce aren't likely to swing votes as they're a group of unknowns.
Maybe they have a few medium acts and they're trying to work out what day to place them on by seeing which days have the least amount of interest in them??