I installed this firefox addon called "Collusion" today and tried to test it against various websites I frequently visit. This is a really amazing addon that gives you an insight about what all websites may be tracking your online behavior and creating a database on your behavior patterns.
I also found that VBFroums has the highest linked sites that track user behavior, among the sites I visit. (MSDN forums is the least). I can understand why this difference - since VB Forums shows a lot of advertisements, while I hardly see any advertisements on MSDN Forums. But still the number of sites tracking my behavior is quite alarming. The ratio is nearly 18:2
While showing me advertisements is perfectly OK, since VBForums earns from it and is is the basic source of revenue to keep this site running, I'm quite against anyone tracking my online behavior.
Please have a look at the two graphs below:
It's actually more complex that what I've shown above. I just showed these separately to make things easier to understand.
Each of these sites will then link to other sites I visit and then other and then other.