FB is data mining
They're selling their data mining to advertisers who then target you. Has your spam gone up since you joined FB? I don't know what kind of advertising they have on FB itself since I've never been there.
On a private writing site I moderate, the adbots are constantly targeting us so we play with it and will write long posts with ridiculous crap in them just to see what ads pop up. We've had a blast with the adbots. I'm thinking of giving them names.