Pedantically, it's a more market-oriented approach. A democratic approach would be if everyone got one vote (not proportional to how much money they were willing to risk), and voted on which drugs they thought should get funding, and the rest got nothing.
Forgive me, this is a personal pet peeve of mine :)
The difference between one-vote-per-person and a vote proportional to the amount of money you are willing to risk, is a significant one. So I suppose Thinkable is halfway between the plutocratic and democratic approaches?
As an aside (tangent to your comment about the rest getting nothing), I don't know what Thinkable does if a campaign doesn't reach its funding target: Whether the money is restored to the sponsors or the researchers simply have to work on a smaller budget (maybe once a minimal funding threshold is passed).