All of the funding that goes to proprietary software could, in principle, go to Free Software; all of the funding for copyright restricted music and educational resources could, in principle, go to works licensed with Creative Commons.

How is this wrong? Kickstarter, IndieGogo and similar projects have boosted the funding of FLOSS software and CC artworks/educational works significantly. Snowdrift.coop is simply an extension of that model.

The 'winner take all' properties of Snowdrift.coop are overstated. If you think a project is raising 'too much', you're free to compensate by reducing your stake, although this will nullify the incentive effect of your contribution. There is no way of escaping this - the same change in incentives happens on Kickstarter when "the goal" is reached. Here, the "goal" of contributions is fuzzy and entirely determined by funders' choices.