sopu
The comment there is really about others I've seen who, imho, aren't that talented, but get attention before they are good bloggers.
We take a 3% cut on cash out. If A gives $1 to B and B gives $1 to C, there is no fee. If C cashes out, we remove our fee and any overhead of moving money in and out of the system. The worst case overhead ends up being a fraction of the overhead of just using paypal.
We have already seen lots of P2P usage of this (paying for coffee or gifting a beer for a friend), and heavy use in microgiving donations to non-profits. As applications build on top of twitter, we expect people to pay for them using us.
We've already made an API for these transactions: http://tipjoy.com/api
Note that you took the step to integrate your phone with twitter, and accepted that a DM = an SMS. You can turn that off.