Google (Nasdaq: GOOG) has tuned up its search engine once again, but this time instead of shaving a couple of precious microseconds off its response time, it's decided to adjust some back-end systems in a way that changes the kinds of results people get, depending on who they are.

Google users who are signed onto a Google account -- that is, a Gmail account, a Google+ profile, etc. -- will see search results culled not only from the Web at large, but also from information contained in their personal Google profiles, as well as info their friends on sites like Google+ have decided to make public. So for example, if you do a search for "Disneyland," you'll see Disneyland's own site, as usual, but you might also see photos of Disneyland that your friend posted and tagged on Google+ a few weeks ago.