Adele becomes just the sixth act to reach No. 1 on Billboard's Social 50 chart since it launched on Dec. 11, 2010 as the diva skips 3-1 in her 49th week on the tally. She follows Justin Bieber (38 weeks), Lady Gaga (11 weeks), Rihanna (six weeks), Selena Gomez (one week) and the Black Eyed Peas (two weeks). During the tracking week, Adele garnered a big 161% gain
in Facebook fans and a 19% jump in Twitter followers.

The Social 50 chart's rankings are determined by activity monitored on YouTube, Vevo, Facebook, Twitter, MySpace and iLike, using a formula that blends weekly additions of friends/fans/followers along with weekly artist page views and weekly song plays.

Adele debuted on the tally dated Feb. 12, 2011 at No. 44, eventually breaking into the top 10 on the list dated Sept. 3. That was the same week her single "Someone Like You" flew from No. 51-34 on the Billboard Hot 100 chart, shortly before if jumped to No. 1 on Sept. 17.

Since Oct. 15, Adele has ranked in the top three every week, finally bumping Justin Bieber out of the No. 1 slot this week. He slips to No. 2, though retains a bullet.

Elsewhere on the tally, singer/actress Zooey Deschanel debuts at No. 25, likely owed to the viral video she recorded with actor Joseph Gordon-Levitt. The pair's rendition of "What Are You Doing New Year's Eve?" was uploaded to Deschanel's YouTube channel on Dec. 28 and has since logged more than 8 million views.

Back in the top 10 this week, Rihanna slips 2-3, Shakira's up 5-4, Lady Gaga rises 6-5 and Katy Perry is up 9-6. Pitbull moves up 8-7, Eminem falls 4-8, LMFAO descends 7-9 and David Guetta returns to the top 10
(14-10).