Indeed, and that's quite a difficult question to answer. It obviously depends on a range of criteria: team, team and team and then track record, supporting mentoring team, partnerships already made, investors already on board, marketing and sales rep, etc. Swogo, Fuel Up, Twoodo, Alive Shoes, 7write, Kinems, iLost, Presentain, Teach'n Go?
Yet another example of the the lean startup methodology applied to everyday life and business issues. The Minimal Viable Event. Great concept. As always, go lean.