The +1 widget on the search results page and other 1st party pages is different than the +1 widget for 3rd party publishers. 3rd parties have to use an iframed widget to prevent click fraud.
Edit: you can. This example [1] has opacity:0.3 so you can still see it. It seems as though it would be trivial for an attacker to put the +1 button over every link on a page. You may even be able to have one tracking the mouse cursor.