You have to work past some initially misguided, romantic illusions.
I saw this theme in (at least) three of the talks.
Andrew Mason spoke of moving from the abstract, wishful-thinking, crusading original vision of the ThePoint to the concrete, feedback-enhanced, tangible-returns model of Groupon.
Dalton Caldwell, founder of Imeem, contrasted the wide emotional appeal of remake-the-music-industry startup concepts with the hard numbers and legal environment that makes those same dreamy businesses impractical.
Brian Chesky of Airbnb showed that even with their basic concept in place from the start, and a series of creative launches and early media coverage, getting both their offering and messaging just right for eventual hypergrowth took lots of detours, time, and tweaks.
It's easy to quit when things aren't going well and you don't have conviction.