Isn't that fraud? (unless you buy something)

I can't imagine you'd be put in jail for a click?

If you as a webmaster told your users to click on ads however, you'd at least get your account suspended.

If any user tells me they clicked some ads to generate some revenue, I tell them politely to stop doing that, and only click if they're genuinely interested in the advert.

I think it's a very small minority though.

I don't willy nilly-click on ads, but I make an effort to pay more attention to them on sites I enjoy. If they fit into something I'm interested in, I'll click.

No, but I do donate.

Unfortunately, I never can seem to find a donate button on mibbit.

I'm actually thinking of showing a [donate] button to people who block the adsense, which seems like a useful step.

I did try a donate button for a month or so last year, but it did absolutely nothing. It's much more useful for me to have happy users telling others about mibbit than giving me a donation, so that's what I tell people to do who ask about donating :)