I read a post where Robert Bowling basically said (blamed) that it's Sony's business to protect the online integrity of their game. Later on he went on to complain about how development studios have a budget and time schedule; thus, implementing more security features was not feasible for them.
It's quite obvious - and has been obvious - that MW2 was a cash out. IW threw it out to die with the some very horrid post-launch support.
Treyarch really proved themselves with Black Ops. And some of you may not like Halo, but look at how Bungie supports their game: not necessarily with constant updates, but with how carefully they monitor and structured their online infrastructure. They care about the integrity of their multiplayer.
Unfortunately, everyone will still throw themselves at MW3, but I'm going to wait for IW to prove themselves.