Google’s been busy lately, but one of the more interesting products came Wednesday with the release of My Search History. It’s a service that allows Google to store an archive of your searching history – which Web pages you clicked on when using Google, when you clicked on them and how often. Conceptually, the idea is not new. Yahoo unveiled something similar with My Yahoo Search in October. But as Chris Sherman notes in his excellent overview, Google’s service is more tightly and smartly integrated with Google’s regular search engine. As with Google Desktop Search, once you activate My Search History and log in, the service works invisibly in the background, recording what you’re doing and then presenting you with results when it thinks they are relevant. If you’re doing a standard Google web search on South America vacations, and Google sees that you’ve visited relevant web pages before, it’ll pull them from your history and stack them above your regular web results. It’s a great concept.

“It’s useful to be able to see what you’ve done on Google and to recall it correctly,” Google’s Marissa Mayer told us.

To Google’s consternation, probably, some of their most innovative products also tend to creep out people. At least one privacy advocate has already branded My Search History a bad idea, and we had a handful of colleagues say  they want nothing to do with it. The service is totally opt-in, so they have that choice. But, to be sure, My Search History and products like it nudge the Super Google privacy issue — something we’ve been thinking about for some time — to another level. There’ve been a staggering number of revelations in recent months about security breaches and personal data such as Social Security numbers getting released into the wild. A search history is intensely personal — more personal in many ways than your Social Security number ever could be. Will we see security breaches with the personal data that search engines and other Internet companies keep on us? It hasn’t happened yet, ten years into the Internet economy. But will we see the day when a search engineer doing QA work wanders home some night with thousands of personal search histories and has his laptop computer stolen? What happens then? Would we ever find out? Would people care?