you can't really compare volunteering at a local choir / local homeless canteen to big corporations taking advantage of open source projects (which is perfectly legit) and never ever feel like they should contribute more to make open source financially sustainable. There is a reason why major open source projects are backed by companies selling products or services based on the open source project itself.
If you don't want big corporations using your software, change the license. They are not "taking advantage" of Free/open software, they are using it, and don't owe the maintainer for it. It feels very entitled to me (a Free software enthusiast who wishes more authors chose GPL over BSD/MIT). As G.W. Bush said "Fool me once, shame on you. Fool me twice... I can't get fooled again"
