I would make opportunities equal, and then somehow be used.
In Vkontakte, like in the monetization of the featured domain.
From an SEO point of view subdomain profitable, sort of.
And cookies are different, that is site.name/user1 and site.name/user2 together along with the labor and user1.site.name and user2.site.name — and even strain is not necessary.
It is also possible to have different DNS dependent parameters for the subdomains.
In General, I would mail a subdomain to a directory — but we'll see :)