StackExchange Inc. can do little to protect our copyright: they don't hold any copyright on the StackExchange network posts, they merely are licensees of the content.
Reports are presumably acted upon in some way if the infringing website significantly harms their advertising revenue, an act which however is not illegal in itself. Or if the StackExchange Inc. trademarks are abused (does that happen often? I've yet to see one such abuse).
To actually get something done and protect the cc-by-sa content, the only effective solution is generally for the copyright owners (the post authors) to file complaints with the website admins, hosts, registrars, advertisers etc.
Source: experience handling hundreds of infringing mirrors of the Wikimedia wikis (some links).
Update: my first attempt already made some infringing mirror go offline (unless it's a curious coincidence). Make people respect your copyleft work!