I kinda agree with you here. I have not heard of Gittip either before this post came on HN. So I visited it, and upon seeing the front page, I immediately thought that this is like a competition where the rankings of the highest givers and highers receivers were showcased.

I think that the site should show something that tipping the projects is a good idea. (Shooting from my hip here) maybe they should pick out a couple of projects and show how the tipping has benefitted the project?