Google has cycled through a number of attempts to make search results more relevant when you are signed in with a Google account. They tried stars similar to the ones used to designate an email message as important in Gmail. Eliminating a specific result from the results you see on the page was another path to personalizing results. They even tried a search wiki concept where you could add notes about a specific result. While I tested all of these features, none of them really made sense. I don't know about your search habits, but when I go to Google to search for something, my goal is to find what I'm looking for and get the heck out of there.
Search behavior like mine doesn't lend itself to spending lots of time annotating search results. My gesture of interest in an article typically extends no further than the fact I actually clicked on the result. When Google first announced their new Google +1 effort, I was equally dubious, because it encouraged clicking a button (like the one pictured below) in order to vote for the quality of a particular result.
In concept this is great, but you can't reallly know an article is worthwhile until you've read it. So here again, Google is trying to get you to interact with a page on Google.com you'd rather leave to arrive at your final destination. Fortunately, Google wised up and made +1 something you can easily use.