YouTube’s 20 Most-Shared Ads in December

1. "Rewind, YouTube Style 2012" (YouTube) See if you can name all the references (and guest appearances) in this mashup of 2012 culture. Click here to view this gallery. In the last month of 2012, the most-shared YouTube ads included some favorites from earlier in the year. The most popular was YouTube's own blowout year-end wrap-up/mashup. The hilarious music video, set to the year's...