Constraints (in the form of funding and time) were a large part of YC. Entrants got a low (but livable) amount of money and 3 months to come up with something great. That something would either sink or swim on demo day.(for more on how constraints help creativity: http://ecorner.stanford.edu/authorMaterialInfo.html?mid=1530) Within those constraints, past YC classes did pretty well, and came up with amazing companies. Those that didn't failed quickly, and could go on to bigger and better things. But YC is now throwing those constraints away.
Because the $150k offer is guaranteed runway, it fundamentally changes the behavioral economics behind startups participating in YC. Products no longer have to be demoable by demo day, and startups won't have to think about profitability/funding, in the short term. This means that we should expect YC startups to dream -and fail- bigger in the future.