I visited an article yetserday after finding out about in in a thread and then went back to the main page of SitePoint but could find the article because it must not have been a new article and then just as I was about to close my window, I noticed a heading "You recently viewed.." and underneath it "Why Write For Another Site?"
We actually looked at a full-blown 'MySitePoint tab' where you could find your recently viewed article, saved article, manage subscriptions etc. It was going to pretty complex to implement and we eventually figured that sometimes relatively simple stuff like this is actually the best value.
We certainly discussed that concept at length, and it's still not completely off the cards. We kinda thought that with 5-7 new articles a week (we can publish more but it's hard to keep the quality really high) we weren't sure convinced people would use it.
The good thing about the 'You recently viewed' is it's pretty transparent. If you don't notice it, it doesn't matter much.
I suppose we could write some rules highlighting particular content based on the kind of stuff on your "you recently viewed' list. Do you think that's how the Amazon one works?