Jason said that it was really easy to launch Basecamp because they'd already built up an audience with their blog. Tons of instant PR from people who already wanted to hear from them.
Max (from here, http://news.ycombinator.com/threads?id=maxklein) said that he was going to be writing a blog about interesting, random stuff, so that when he announces something of importance, he'll have people listening. Thus Cube of M.