This is what concerns me, although I think the point is more for the mags to be in a member's possession to where they will be available for scanning. Not necessarily scanned right away unless someone absolutely wants an issue or two done.
I mean, it would be a donate-as-you-want and if you want type deal. It's not like you're being required or even rewarded for doing it. More like, hey I have a few bucks to blow might as well support the site in some way. Again, not everyone will see it this way, but no one is required to donate to the cause, either.
I think overall it might work, but of course may be a point of controversy as well. Also, it's not guaranteed that we'll eventually have enough money(sometimes in the 100's) in the fund for it to be useful.