Where did you get the server-host issue from in the first place ?
I personally will probably at all times have content on my server somewhere that is let's say a bit more, hardcore, than a couple of old geeks/nerds playing doctor with their online dolls.
Do I think I am in any way, shape or form taking a risk? not at all, that would be rather paranoid. Have you _seen_ the internet ?
I highly doubt the situation is any different in the US, regardless of what some lawyer would be able to come up with. Actually I know it isn't,- millions of servers operate in the US with content that would actually warrant what is proposed in this thread without any sort of disclaimer. Somehow I think those might be given a higher priority than our, let's be honest, pretty innocent online fantasy group (where most players are over 25). That is, if the basic premise of cyber-police/cyber-lawsuit thing was even a reality in the first place. The fact is, as long as the american hosters don't publically offer a bunch of new Disney movie bluray rips we're gonna be just fine and not encounter the law in any way shape or form, we're simply not remotely interesting enough for anyone to bother, even concerned mothers of america, who probably have their hands full with sites like motherless (dot com, don't look at that unless you really think you want to

)
Since anybody can just lie and say they're 18 anyway, we're basically buying into the "as long as i told them i'm fine" concept, which, if this whole issue came from a morality point of view to begin with, clearly wouldn't cut it anyway. It is simply a device used to not get blamed for it,- the "damage" (i have no idea how anything ALFA could ever damage anyone, come on!) would already have been dealt.
If it is actually the case that the vast majority of members are adults (even old people

), a good way to show it would be to just remove any notion of a (highly flawed) rating system used to rate films in America, trust the playerbase and DM's, and remove fingers from behinds and placing them firmly back in the ears in which they belong.