Marc Andreessen kind of touches on this in Why Software is Eating The World: http://online.wsj.com/news/articles/SB1000142405311190348090...

The barriers to entry for startups have gone down, and thus there's higher quality startups competing for the same funding. As development becomes cheaper, easier, quicker we are just going to see the bar go up for early stage investment because investors will have more and better options.