Nah, subdomains aren't any different from directories. You can easily setup wildcard subdomains and all of them run off the same code base. I can easily have us

Nah, subdomains aren't any different from directories. You can easily setup wildcard subdomains and all of them run off the same code base. I can easily have username.mysite.com show the user's profile the moment a user signs up. No changes to any servers needed.