[LeBlanc]

1) Yes, here are some marketplace type sites using the WePay API: http://bellstrike.com/ http://www.everribbon.com/ http://www.listcharming.com/ http://www.attendstar.com/

2) You can issue refunds for any payment in your marketplace with the /checkout/refund call. For chargebacks, we 1st attempt to get the money from the payee's WePay account, then from their bank account, and finally from the API application. We do a lot of really cool stuff that reduces the chargeback risk and fraud in general.