You said you partnered with people with email lists and offered them a booth at your event for them sending mail to their list. Do you think this method could be a general way for other startups to get traction?
I do, and it's already used all the time (e.g. DailyCandy charges thousands of dollars for a Dedicated Email for a given city's email list).
What we did was sort of roll our own campaign, trading the positive association with our unique event as well as a booth, signage etc. there for cash-free marketing for us.