Just my 2 cents, but I did not/do not know what gittip is. The above link invites me to sign in using github, I'm extremely cautious of logging in using github anywhere as my personal account is also my work account.
Any page where I can land and be asked to log in should do a better job of saying what you do, especially where trust is involved.
Definitely could do a better job of converting traffic. Don't feel like I have that nailed yet. :-/