I wouldn't start a company with someone where the relationship wasn't based on fairness. If I don't trust my potential co-founders enough to share the company equally, they shouldn't be my co-founders.
EDIT: s/your/my/, s/you/I/ ... my personal position may not be best for you.
Except that T61 destroyed their usability in the name of a shiny new design, and drove away a ton of active users. I loved the old T61, but find the new site completely unusable.
Founder of Twitpay here...our RT2Give service, which we're launching as part of this transition, will be clearing the payments directly, not with PayPal. Our personal payments service (twitpay.me) will continue to use PayPal.