The tracking is bad, even when you know about it. Sometimes my friends will send me something on Amazon with ridiculous reviews or it's just a crazy item (e.g. the $5 million book on Amazon or the Nissan car). Now Amazon thinks I like that thing and want to see similar items, when all I really did was go to the page, laugh, and go on my way.

I know now to open up those links in incognito windows, but every so often I still have to go delete my "viewed items" on the site so the prediction becomes relevant again.