I would make opportunities equal, and then somehow be used.
In Vkontakte, like in the monetization of the featured domain.
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From an SEO point of view subdomain profitable, sort of.
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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.
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It is also possible to have different DNS dependent parameters for the subdomains.
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In General, I would mail a subdomain to a directory — but we'll see :)