We knew that Boxee is adding paid content, so hearing that they're working out a payment system is no surprise. What's interesting is that the company Boxee will work with, Vindicia, was picked because it'll play well with mobile devices:
Vindicia's flexibility also makes it possible for us to enable payments on our website and across mobile platforms like the iPhone, Android and iPad. Boxee's eventual expansion to these platforms will pave the way for universally accessible content no matter where a user is (we love this idea!).