Instead of the +1 button being displayed by default, it is now hidden until you place your mouse cursor over the search result. Then the +1 button will show up and let you click on it.
Here is a picture of the animation seen when you mouse over the search result, which brings up the +1 button and the right gray arrow bar on the right of the search result:
Then when you mouse over the +1 button, it will turn blue and when you click on it, it remains blue.
This seems to be an effort to reduce the cluttered Google search results interface.
Postscript - Google sent us this statement about the change:
As we simplify the look and feel of the search results page, we wanted a way for users to easily see the +1 button when it’s most useful to them, such as when they hover over a result to recommend it or when a result has already been +1′d. By showing the +1 button when people want to click it rather than next to every result, the +1′d results stand out more. So far, this change has had an insignificant effect on +1 usage.
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