y'all be forgetting that, IMHO, the "regular" merriweather stage will be vfest's second stage. the festival's "main stage" will be set up out in a parking lot, will be all-GA, and will potentially be able to accommodate more people than the "regular" stage. so while blink+weezer might easily sell out merriweather's regular stage, they'll need help with an expanded GA-only parking lot stage.
not necessarily. when HFStival was held there, the main stage was the ampitheater with smaller acts in the parking lot.
I think the best set up would be a combo of two stages in the lot going rapid fire one after another (they do this for warped tour) but this would drastically cut down on attendance unless a 3rd stage (the pavilion) was used.
Ultimately, as Vfest did last year, there was no real main stage or side stage really as far as acts went, at least not for the last few bands.
Also, to comment on gaaaah's comment, i dont see that Seth would necesarily only book the amount of bands he thinks will sell X amount of tickets. not only is he trying to build a brand, but there will be something to make up for with the venue change and all. plus, if the fest is 2 nights, with Weezer and Blink playing one night, someone has to play the other.