As one more slap in the face to the pioneer of the social networking phenomenon, Facebook has become more popular than Myspace here in the U.S.

Earlier this year, ComScore Inc. reported that Facebook recorded almost double the number of worldwide visitors in December than social networking pioneer and longtime market leader MySpace.com Inc. However, when it came to the United States, MySpace has clung to its leadership position.

That is no longer the case.

Online researcher ComScore released a report this week showing that five-year-old Facebook attracted 70.278 million unique visitors in the U.S. in May, just ahead of MySpace's total of 70.237 million. In April, Myspace had nearly 71 million unique visitors compared to Facebook's 67.481 million.

Worldwide, Facebook had more than 307 million unique visitors in May while Myspace attracted less than half of that total -- 123 million.

Myspace remains a go-to site for the tween and teen set, but Facebook has been getting significant growth from those closer to eligibility for an AARP membership.

In February, the social network's audience of people over the ripe old age of 35 increased by 23% compared with the same month in 2008, according to a report released today by Hitwise Pty., which also measures online traffic. While Facebook was launched to serve college students, the network over the past year or so has broadly expanded to include many middle-aged folks.

And those new older users have been doing great things for Facebook's numbers.

Earlier this month, a report from the Nielsen Co. showed that in April, Facebook users spent 13.9 billion minutes on the site, a dramatic hike from the year-earlier total of 1.7 billion minutes. The 700% increase let Facebook easily maintain its place atop the social networking business.

MySpace, according to Nielsen, came in a distant second place as users spent nearly 5 billion minutes on the site during the month.