Metrics firm ComScore reports that 132 million unique visitors logged onto Facebook in June 2008, up from just 52 million in June 2007. 117 million worldwide users visited MySpace during June 2008. Its Facebook's first definitive traffic victory, from a source advertisers actually pay attention to, over MySpace. Way down on the list at No. 6 — past the fast-growing Hi5, past still-kicking Friendster — there's AOL CEO Randy Falco's $850 million social network, Bebo, which saw 24 million visitors in June.

Record label EMI may have tired of suing individual file sharers for copyright infringement. But a number of music-industry plaintiffs, all partners and subsidiaries of EMI, are suing social network Hi5 and advertising startup VideoEgg in New York Southern District Court for copyright infringement. According to the complaint [PDF]:

In the month since San Francisco-based social network Hi5 launched its platform for independent applications, users have installed widgetmaker RockYou's applications 2 million times. The most popular third-party application on MySpace only has 100,000 installs. The difference? Hi5 links to its application directory from user profile pages and allows application makers to send notification messages to users. Those simple interface elements allow Hi5 users to see which applications their friends are using, which then prompts them to add them, too — the main factor in their spread. MySpace is still working on those kinds of tools, reports VentureBeat. Facebook built those types of innovations into its platform nearly a year ago.

Now we know why Bebo's so eager for more cash. It needs more servers. According to Pingdom, Bebo has already been down for 12 hours and 28 minutes so far this year. Check out the full chart to see how 13 other social networks have fared so far.

Creative Capital got ahold of the December 2007 ComScore numbers for the top social networks in the U.S. — and they are, on the whole, not good. Engagement — average minutes spent on the site per visitor — is down for MySpace and Microsoft's Live Spaces, but up for almost all the other sites. Unique visitor growth is ominously low for MySpace and, in the last three months, LinkedIn. Hit the jump to see the numbers for yourself.

VC blogger Fred Wilson gives Google and Yahoo too much credit: He's taking their "Inbox 2.0" initiatives to turn Gmail and Yahoo Mail into social networks seriously. He 's put together a chart comparing the "social graphs" — we think he means "number of users" — of some popular social networks versus Microsoft's Hotmail and AIM.com. Wilson estimates that Yahoo and Google, which aren't actually on the chart, have about 250 million and 60 million users. Here's the chart.

According to a source, blog-software company Six Apart has joined as another partner for Google's OpenSocial platform. For those of you keeping count at home, don't bother. The list is surely to grow as word gets out. Social network Friendster, for example, wasn't asked to join the Google Gang. The pioneering social network begged to be included after a story leaked on TechCrunch. Google's secrecy is making the whole "open" affair less than transparent, as different names leak to different reporters. Here's a list of media outlets and the OpenSocial partners they list.

Apparently, overseas, there are social networks other than Facebook and MySpace. Who knew? Read/WriteWeb mentions that social net Hi5 which tallies 35 million uniques per month according to ComScore, making it competitive with Facebook. And yet the name will draw blank stares at a Silicon Valley tech meetup. Like Google's Orkut, Hi5 is huge overseas and virtually nonexistent in the U.S. Hi5 even launched a developer API in August, but got scant coverage from the Web 2.0 crowd. The bias, of course, is partly driven by economics. Tapping overseas advertisers is tough, and so developers planning to build ad-supported websites and applications naturally turn to U.S. markets. But media myopia is a factor, too. Until magazine editors' teenage daughters start using it, Hi5 is likely to remain invisible.