The info on the WHOIS seems to indicate an apartment or office building if the street view is pointed correctly. And the site ran entirely off donations (and probably subsidy from a real business) so what's to blackmail?
I think something illegal posted on the site may have come to the notice of any authority and he got some mail. So got spooked and closed the site.
p.s. I think site owners should not be held responsible for user's wrong doings.