Being a very big fan of StackOverflow, I was just thinking that it would be really great if there was something like StackOverflow for webmasters.
I did some searching and it seems that there aren't many popular websites for webmasters. At least not as popular as StackOverflow is for programmers.
I imagine that, on the business side, it should be profitable enough to be considered. The topic is very popular and would not just be among webmasters. A lot of people are interested in this, basically anyone who has a website or a blog.
There are so many things that can be advertised on such a site (web hosting for example, among other things), that it could eventually be more profitable than StackOverflow and ServerFault. ;)
I think it can be really useful, there are so many topics related to webmasters, e.g. hosting, search engine crawling, online advertising, SEO, moderation... you name it!