not coming from proudhon, just from experience...
these are some possible problems (in no order at all):
a) the issue of revocabality. anarchists donate to a lot of projects, but as far as i can tell they're mostly either projects and/or donations that are short term, or that the donaters are closely connected with. this provides a flexibility and accountability that longer term projects of distant people don't have.
b) anarchist infrastructure, without anarchists to actively defend it, is worse than nothing. it takes our resources and provides an easy target for the state. the fact that anarchists have (with sweat and blood) carved out and held space in athens is due to conditions that don't exist here, and it's hard to know how the relevant conditions could be recreated/transposed.
c) the power relationship between fund holders/mutualist bankers and other anarchists would be complicated and contradictory. this probably isn't insurmountable, but it's a thing.
d) connected to b, anarchists in the u.s. are not that great at defending. there's an argument that if we had more stuff to defend then we'd get better at it, but who knows. (there are benefits to letting shit go and moving on, but there are definite downsides also. but that's a different discussion.)
what do *you* think?