Was just asked that question on the original post, our response: We applied to each of the conferences directly. At Disrupt, they liked what we were doing but weren't 100% sure about putting us on stage. We were persistent and they offered us a cocktail table. For Launch, Marc responded to Jason Calacanis' post on hacker news looking for innovative companies and we applied directly to the DEMO scholarship program. During our interview with DEMO we told them we were bootstrapped and couldn't pay for even a partial scholarship.

A big part of it this of course is selling your company's vision to them when they are evaluating you. If they get excited by the vision, they'll want you to come to their conference.