Big consumer brands are thinking of this year’s Summer Games as a way to get people talking on Facebook, in particular, about them. Four years ago, it was very much about paid media. But now brands foresee much chatter during the two weeks. By the end of last year, some 794 million people visited Facebook each month, and each spent an average of 377 minutes - more than 6 hours - on the site, according to comScore Inc. In 2008, Facebook had just 145 million users.