That Tom. What a wildcard!

Top US social networking site MySpace.com's unique audience (UA) was up 7 percent in May compared with May '07, but second-place Facebook's was up some 83 percent from a year ago, according to custom lists compiled by Nielsen Online, writes MarketingCharts.

LinkedIn, continuing its trajectory, increased its unique audience 146 percent from 2007, reaching nearly 7.7 million in May, compared with 3.1 million a year earlier — and retaining its No. 4 position after unseating Windows Live Spaces in March.

MySpace's unique audience totaled nearly 60.7 million in May, compared with No. 2 Facebook's 26.0 million.

Top 10 Blogging Sites

Google's Blogger remained atop blog site rankings with 39.3 million unique visitors, up 40 percent from 28.0 million in May '07:

WordPress was again up — an impressive 170 percent from May '07 — increasing its unique audience to 17.1 million.

Sixth-place HuffingtonPost.com also maintained its impressive growth — 255 percent — from a year earlier, moving up from seventh place in April but still down from its fifth-place ranking in March.

Meanwhile, AOL Sports blog The FanHouse, having burst onto the top 10 scene in March, moved down to the No. 7 position (from No. 5). It had 3.9 million unique visitors in April, compared with nearly 4.4 million in March.

Gawker, at No. 10, increased its UA to 2.0 million from 851,000 a year earlier, a growth of 137 percent.