Killzone 2 online D:?

So I finally found a cheap copy of Killzone 2 for my PS3 at Blockbuster. I quickly got home, played through a few campaign levels, then tried online multiplayer. There were a grand total of FIVE people on, and 3 were in a match with the little lock logo. It was on Memorial Day, so was that it? I thought this game was insanely popular and would have copious amounts of people online. :-/