Cost and capacity to do this aside, should one archive a site that permits user contributed content <i>text and/or multimedia content</i> I foresee a legal conundrum. That which may be considered acceptable speech and/or multimedia today could be deemed hate speech, libel or even illegal by a country in a few years or decades. Content deemed illegal in the future also becomes illegal to delete. CDN's and ISP would not want to deal with the legal conundrums and would just boot archive sites all together.