Much better is to just nullroute their netblocks at your router. That's what I do.
You have a lot of determination! Kudos.
It's pretty simple, really: Edit Preferences -> Privacy -> "Firefox will: Use custom settings for history" -> <uncheck> Accept third-party cookies. To add an exception, click "Exceptions..." on that same page, type the domain name, and click Allow.
You can still receive normal cookies, but now third-party sites can't track you unless the sites you're visiting are sharing data server-side.
I'm sure facebook has myriad nefarious ways for tracking everyone you interact with regardless whether they have an account.
And do we need to point out Double click got caught tracking individual users and lying about it over 10 years ago.
Some sources would obviously be helpful, but I don't think anyone is kidding themselves about what's going on.
I am working up to doing the same for Google. I might transparently proxy google.com/search to Scroogle just so browser search bars continue to work.