That's got to be part of Facebooks's long term business model.
For RedSoxFansWhoAlsoWearRedSocks.com, targeted advertising is fairly easy, but for sites with a broader audience, like nytimes.com or salon.com where personal information is needed for targeted ads, Facebook already has this information and can sell a connector to you, the nytimes.com ad manager.
Even if I did visit RedSoxFansWhoAlsoWearRedSocks.com a lot maybe I already have enough red socks. Which has happened to me recently in this example.
I have been researching a new laptop for the past three months. Finally I decided on getting a ThinkPad x201. Not once did I see any laptop ads on any sites I visited except the specific niche research sites. Now I see Lenovo ads everywhere. They're on slashdot, facebook, boy genius reports. These ads would have been useful to me before my purchase, not after.
My point is that using the topic of the site alone isn't enough. Even on facebook, which probably has the most detail about me than any site, they still get the ads wrong. I rarely find them relevant to my life and needs.
By the way, besides being creepy, I'm not sure that Facebook's plan is so bad. Replacing annoyingly bad ads with better ads that know more about me is creepy, but at least the ads are better.
The way I explain Facebook's plan to non-techies, btw: Imagine you have a friend called Jenna that has a birthday next week. Now, whenever you visit say, Amazon.com, they'll have ads saying "Jenna's birthday is next week, why not buy her this nice book?". Creepy, but that's where we're headed.
For RedSoxFansWhoAlsoWearRedSocks.com, targeted advertising is fairly easy, but for sites with a broader audience, like nytimes.com or salon.com where personal information is needed for targeted ads, Facebook already has this information and can sell a connector to you, the nytimes.com ad manager.