Naming and shaming - whilst looking like a proper thing to do - is a dangerous game. Word it wrong and find yourself on the back end of a libel claim. bummer init?
Oh, missed that bit. Presumably you'd contact the company first, to ask for their response. Some/most may well not be aware this is happening.
(e.g they pay some ad network, without being fully aware where their ads are being placed...)
As for going public, I'd like to think a screenshot of the company's ad at the top of thepiratebay.com would be quite a good libel defence. But perhaps not sufficient.
Anyway, I'm pretty sure this stuff has been looked at, and it would be good to read some papers. (Will do when time permits).