While Justin Bieber continues to hold down the fort at No. 1 on the Social 50 chart, Britney Spears makes the largest positional leap up the tally, flying 21 spots to No. 22. No doubt the excitement stirred by last week's release of Spears' new single, "Hold It Against Me," generated buzz in the social network space.

The Social 50 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/followers along with weekly artist page views and weekly song plays.

Spears saw a 16% increase in new week-over-week Twitter followers, a 2% jump in Facebook fans and a 126% gain in MySpace fans. Additionally, her YouTube channel posted a 27% gain in subscribers and a 124% rise in views (compared to her new followers/views generated last week).

After the online community was set ablaze with chatter about "Hold's" release last week, does a No. 22 placing for Spears seem low? Not necessarily.

The Social 50 ranks acts based in part on how many new friends/fans/followers they gain in a particular week, as opposed to simply their total mentions on Twitter or number of times they were tagged or commented on Facebook. So, at the present, Spears seems to be energizing her sizable fan base, but we'll have to wait and see if she can continue to move up the chart in the coming weeks, gathering new friends/fans/followers.

But let's get back to the top 10 this week. As noted, Bieber is steady at No. 1. Right behind is another non-mover at No. 2, Rihanna. Akon jumps 6-3, the Black Eyed Peas hold at No. 4, Lady Gaga falls 3-5, Eminem moves down 5-6 and Taylor Swift returns to the top 10, climbing 11-7. Katy Perry also slides 7-8, as does Linkin Park (8-9) and Shakira (9-10).

The top debut this week comes in at No. 31 from Dave Matthews Band, while Boyce Avenue -- a popular act on YouTube -- arrives at No. 34. For the latter, the trio is up 65% in week-over-week YouTube subscribers and 26% in YouTube views. That's not entirely shocking, since the group posted a new video last week -- an acoustic cover of B.o.B's "Airplanes," featuring Hayley Williams -- which has generated over 500,000 views.

Madonna is also a new entry this week, at No. 42. While she's been off the music charts for a while, her name was back in the news last week thanks to CNN host Piers Morgan, and his "ban" on the singer from his new chat show. Madonna's official Facebook page garnered a 23% week-over-week gain in fans.

Daft Punk re-enters at No. 43, as does Kanye West (No. 46) and Justin Timberlake (No. 47). The final new entry comes from Nickelback at No. 49.