As is only natural this makes me return to thoughts of niche markets… You can make a Facebook or a MySpace, but that is pretty broad and I presume that there will be a struggle to gain users. If however, you limit the sites capabilities and make a specific function for the site to perform, it should appeal to a more specifically interested and hopefully "truer fan" of the site.
The future of web is pointing towards a very particular user that should and will be able to find an exact match for what they are looking for in regards to anything. All that we have to do is find a need, fill it, and hang on.
Also we should figure out where revenue can come from without the clutter of ads. (Another day perhaps.)