Another rumor, but this one apparently came from Robert Bowling, Infinity Ward's community manager (aka FourZeroTwo):
If you go to the Infinity Ward Modern Warfare 2 forum, there's posts saying that there are no dedicated servers for PC.
Also, this podcast: http://www.ustream.tv/recorded/2369799
Robert Bowling starts talking at 1:38:00 (1 hour mark). A few minutes in, he starts talking about how there will be no dedicated servers.
Not only IW, but the forumers there too.
Someone is so pissed that they started spamming the forum with porn (calls himself 4chanpartyvan)
Everybody else is making whining threads, threads about their pre-order cancellation, petition threads, etc. As far as we know, it could be truth or a misunderstanding but look at the damage it caused!
Go to the forum yourself but be warned; there is porn.