Hmm, my answers are totally different for everything, it looks like! XD Of course, this is pretty much all theoretical--I have only rarely contributed to any such projects in the past, and I really don't have much disposable income right now. But let's see if I can break this down.

I'm much more likely to comment and contribute money online than in real life. This is partly shyness and partly the fact that, like others, I don't really carry much cash in real life (though I think I filled in poll answers as though I was carrying cash). I don't find it inconvenient to contribute money online because most people use PayPal, and while I'm not a fan of PayPal, it's there.

I think that I would be too intimidated by a performance artist to approach or tip (see: shyness).

I'm less likely to comment if I don't have anything interesting to say, even though, as a writer, I'm thrilled with any comment that isn't spam!

I don't think I've ever seen an artist with a tip button. Except webcomic artists, I guess, but for webcomics I'm much more likely to buy a book or other merch (that is, I've never sent a webcomic artist a pure donation). I imagine if I was blown away by an artist's work and there was a tip button, though, I might donate.