Someone at BarCampBlock yesterday suggested that in the past >15 years, vc-backed startups of all types accounted for 23% of successful exits, while focusing on tech-specific startups raises that number to 46%. It sounds possible, but a source wasn't provided - it'd be interesting to determine how successful these 'successful exits' were, and if the size ($) of the exit is correlated to the presence of VC. I imagine it would be.