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In an interesting move, Google has removed the +1 button from its search results page. The button only shows up when a user hovers the mouse over a particular result, now.
Previously, there was a +1 button next to every search result, enticing users to highlight the links that they found interesting or useful. There's no way of knowing how popular +1 button has been, either on Google Search or elsewhere.
The move guarantees a cleaner results page, which has always been a huge goal at Google, but it also means that the button is less visible and, presumably, less clicked.
Considering the amount of effort, and money, Google is putting into Google+ along with the +1 button, the move is fairly surprising.