How do you see that happening? Part of the reason for the pricing on the APIs was to ensure that more people saw the ads. I know I never see them when I use BaconReader.
Monetizing something like Reddit is always going to be a struggle, especially since the Reddit crowd is more tech-savvy than the Twitter and Facebook users, thus more likely to use ad-blockers.
I honestly don't know of a way that a social networking system can ever have a near-universal scale and still make money. Sure, a niche community that relies on contributions from its members to offset development and hosting could work, but not Reddit or Twitter with they way they're going. FB is still going pretty strong, but last I checked, 70% of the main feed content I saw were ads.