The latest comScore stats for May 2006 show how
fast social networking sites are growing, but YouTube in particular is displaying spectacular
growth. As comScore noted in its monthly report:

“There seems to be no end in sight when it comes to the popularity of social
networking sites. Myspace.com surpassed the 50 million unique visitor-mark in May, an
increase of seven percent since April. In addition, Youtube nearly doubled its traffic
in May, reaching 12.6 million visitors, while Classmates.com reached 14.7 million
visitors, and Facebook.com captured just over 14 million visitors.”
(emphasis mine)
According to comScore YouTube had 12.6 million unique visitors in May (up from 6.6M and so putting it just
outside the top 50 properties on the Web), Google Video 7M, and Yahoo! Video 4.2M.
YouTube was in fact the fifth most “Gaining Property” across all the sites
comScore tracks, by percentage change in unique visitors, from April to May! Here’s the
trend chart, comparing YouTube’s success with the far more static growth of Yahoo Videos
and Google Videos:

Alexa.com shows a similar trend, but suspiciously their stats have YouTube with the
same reach as MySpace (which obviously isn’t right):
I’d be interested to see Hitwise’s chart for May 06, because
last time they did one (in December 05) they had Yahoo way out in front – but at that
time YouTube was just starting it’s big push:
Summary
So in the space of just 6 months YouTube has not only overtaken Yahoo Video as the
most popular Web video-sharing service on the planet, but it’s now approx 3 times as
big as Yahoo’s product! That just shows (once again) how quickly the status quo
can change on the Web.