Keep in mind this is a government agency that does the screening here. I knew someone who was not a "prominent person" in their field who got an O-1 visa with the help of their VC investors / angel investors.
On official US Govt site, it says you need an award, e.g. nobel prize for O1. But that is a complete exaggeration as many people have rather average creditentials getting the O1. Having a good degree is enough for several people. Everything in addition helps.
Plus if you think about it, if you're in YC, getting PG or Vinod Khosla or Ron Conway (the YC VC people) to sign a letter talking about your "genius" will probably go a long way.
Also, many in government are entirely aware that the visa system is broken and do all they can to change it without legislation. Changing the criteria for the O1 is a simple way of freeing up more visas.