This is a model which seems to work for donation campaigns for FOSS projects. I wonder how much this scales though... if everyone does that, is there a point where users will be fed up with it?

I'm not sure the "bubble" comparison properly applies. Still there are indeed signs of the Open Source movement getting in troubles. It'll be all the more important to stick to the Free Software values.

Clearly inspiring... this project really went from dying to skyrocketing. I'd like to see more of those.

Indeed, there's more funding available. It's becoming a maze though and PR shouldn't be underestimated.