It's been talked about before, but the biggest limitation is that most forums allow spaces (or special characters) in peoples names. For example "Michael P" would not form a valid URL as described above and depending on if there are others with the same name, but when you take out the spaces and non-URL characters may end up with the same URL string.
I've been looking into possible code alternatives while some people have used htaccess rewrites to accomplish this.
Please do not PM me for support or sales questions. Thank you for your understanding.