I have had some clients ask if they could host with me without buying their own domain. I was able to convince them of the benefits of having their own domain, even if they were just running a fansite. Still...different clients, different needs. I think it may be a seller, just not a *big* seller.
You might try offering subdomains on a few different domains - themed, sort of. That would let buyers choose which "theme" they wanted, but also allow for duplication (names, football teams, that sort of thing.)
The one thing you'll want to watch out for is people spamming off of the subdomains. While I don't know that any business would want to host off of someone else's subdomain so there's not the possibility of a business having their reputation tainted by association, if one client spams, it's much easier for the recipients to assume that anyone on that domain is also a spammer.
There's one thing to do with your "drunk domains"...! Use them as alternatives to those who want a hosting account, but don't want their own domain!