I think certain companies have found "obscure provisions" (not necessarily loopholes) that allow them to not put "this is not spam" in the footer, and probably something like having kept documentation of every address being stored with the original reference request.
Though I'm too lazy to look on my other account, I think Radio Shack comes to mind.
What makes it worse is many sleazy companies put the "Footer" there but bogus, because when you click it to opt out, they go "Yay! Someone read this! Sell this number to our "partner" ! Then they can get four more spam!"