I get this feeling all the time after following a link from reddit. I just hope they can deduce from the referrer that I am not actually interested in purchasing life-like male self-stimulation products.
That's why I use different browsers. Chromium logged in with my Google accounts, Firefox for everything else.
I go one step further, and put chromium in incognito while logging in to google services. The only problem is clicking youtube links from gmail/gtalk - I have to remember to paste them in to firefox.