Following a note from a Guerrilla staffer on the US PS boards overnight that said promo copies of Killzone 2 won't work online, the company's officially said that it isn't true.
Promo copies won't work at the moment, SCEE told Eurogamer today, as the game's servers aren't yet operational. Killzone 2 launches on February 27.
The whole topic arose because promo copies are being sold on Ebay.
This doesn't mean you should buy one. Wait and get a nice game with a nice box.