I'll say. I've seen some websites that have over twenty activated.
Good thing about Ghostery is, once you've disabled a particular tracking program, it's disabled for any website that employs it.
I've disabled so many now, that it's rare for me to check a website and find one that I haven't already blocked. Great tool, and simple to use.
I think the most I have seen at one time was 19. I just told it to blaock everything from the get go.
Just installed it.
AVG anti-virus now comes with something similar, "Do Not Track" and it works pretty well.