Just going to echo something that's been said a bunch - I think having to choose a server to register on is going to be a huge barrier for people interested in Mastodon.

Following the "easiest way to sign up" link takes me to a list of servers with no clear default choice. The top few options all require applying for an account, and are for special interests (Ruby/Anarchism/Animation Professionals). The first "open" server is for the Glasgow area. I think tons of people will give up at that point.

At the same time, enshrining some general-purpose server as the default try-this-first one, would run counter to the core idea of Mastodon, so there's no clear solution to this problem.