Rihanna simply won't give up the No. 1 spot on the Social 50 chart, locking up the crown for a fourth non-consecutive frame. The tally ranks the most active artists on the world's leading social networking sites -- YouTube, Facebook, Twitter, MySpace and iLike -- using a formula blending weekly additions of friends, fans and followers along with weekly artist page views and weekly song plays.

Rihanna isn't the only non-mover on the list -- the entire top five refuse to budge. Justin Bieber holds at No. 2, followed by Lady Gaga, the Black Eyed Peas and Eminem.

Michael Jackson moves up two rungs to No. 6, Katy Perry climbs three to No. 7, Linkin Park rises one to No. 8 and Akon drops three to No. 9. Shakira finishes out the top 10 at No. 10, ascending three steps.

Making a big leap up the survey is Avril Lavigne, who vaults from No. 26 to No. 16 in the wake of the release of her new single "What The Hell" on Dec. 31. She rallies with a 76% increase in new Facebook fans, a whopping 131% jump in Twitter followers and a 98% lift in YouTube fans.

Chris Brown also motors up the list, rising from No. 33 to No. 21 after he was involved in an incendiary Twitter war with B2K's Raz-B. As a result, Brown is up 375% in Twitter followers, the largest increase in that segment on the chart. Additionally, Brown's "Yeah 3x" single continues to find success on our charts. This week, the tune holds at No. 19 on the Billboard Hot 100 for a second week and steps 14-13 on the Mainstream Top 40 radio airplay tally.

Taking a tumble this week is Enrique Iglesias, who dives from No. 7 to No. 22. Last week, he flew up the ranking from No. 21 to No. 7 in the wake of the Web premiere of his video for the racy "Tonight (I'm F*****' You)."
However, he was unable to sustain the momentum from last week's gains in friends/fans/followers, so he slides back down the list.

P!nk re-enters the chart (No. 27) as her new single "F**kin' Perfect" is finding ground at top 40 radio. The track might debut on the Mainstream Top 40 chart in the next few weeks.

Rock band Paramore also re-enters (No. 36), powered by the buzz of the soap opera-worthy drama of the group's recent lineup change that continues to make headlines.

Joining the re-entering crew as well are Bob Marley (No. 43), Nelly (No. 44) and Britney Spears (No. 49). Two new entries grace the chart this week, as Muse and Miley Cyrus bow at Nos. 41 and 48, respectively.

Falling out of the top 50 this week: Pomplamoose (of Hyundai's near-inescapable holiday TV commercials), Keri Hilson, Dr. Dre, Flo Rida, Cascada, Demi Lovato, Trey Songz and Avenged Sevenfold.