The difference between professional societies and crowdfunding is that professionals, not the crowd who donate directly, decides which projects to fund. In this sense, I do not see a great qualitative different to government funding agencies --- if you do, please elaborate.
EDIT: And to clarify, in the societies I know, general members do not directly take part in grant decision processes. Rather, the decisions are made by a small panel, possibly together with external reviewers. This is fairly different from crowdsourcing.
It's different from crowdsourcing, but the source and sink for the funds also tend to be more closely related. Ultimately I don't really believe that major initiatives (eg P01-level grants) can be adequately reviewed by anything other than genuine peers.
But by the same token, an exploratory study requesting $30k for field work or sample processing could very well be evaluated by less skilled peers. Actually, I think I'm going to try and shop this to a friend at NIH. I'll fail, most likely, but at least I won't just be whining.
For example, pharma and big donors use the LLS review system as a "study section lite" to hand out grants larger than a typical R01. The paperwork and BS isn't really necessary at that level and just gets in the way. If something like this existed for "lark" projects, inside or outside of NIH/NSF, perhaps more diverse and potentially diversifying proposals would be worth submitting.
To some (fairly large, in the case of ASCO or ASH or AACR, perhaps smaller for LLS or AHA) degree, the dues-paying professionals in these societies are the crowd. I would say they are a middle ground between something like an experiment.com or similar at one extreme, and NIH (which has inordinate purely political input -- ask your program officer!) at the other.
We shan't discuss scams like Komen here, but genuine research foundations can exist along a continuum.
The paperwork burden for an NIH grant (relative to a society grant) is often a large scalar multiple. The accountability is often on a par with, or less than, the typical society grant. It mystifies me why this should be so.
EDIT: And to clarify, in the societies I know, general members do not directly take part in grant decision processes. Rather, the decisions are made by a small panel, possibly together with external reviewers. This is fairly different from crowdsourcing.