Social Networking, Web Traffic | featured news

LinkedIn has hit 50 million users, according to a blog post today, growing from 45 million users two months ago. And according to the latest comScore data, LinkedIn is steadily growing in terms of unique visitors.

If it wasn't bad enough that Facebook bought FriendFeed on Monday and turned on real-time search to better compete against Twitter in the Stream Wars, and is playing around with a lite version that resembles Twitter even more, now Twitter really has something to worry about. Facebook is growing faster than Twitter in the U.S., even though it is more than four times larger.

The global rise of Facebook is nothing less than astounding. In the month of June alone it gained 24 million unique visitors worldwide, compared to the month before, for a total of 340 million unique visitors worldwide. It is now the fourth largest site in the world, trailing only Google, Microsoft, and Yahoo sites, according to comScore (see table below).

Tweetmeme is on a tear. According to Compete, the Twitter-centric link tracker went from nowhere in February, 2009 (with 26,000 unique visitors) to more than tenfold increase in March (to 385,000 uniques). Nick Halstead, The CEO of UK-based Fav.or.it, the company behind Tweetmeme, tells me he is tracking closer to 200,000 uniques a month based on yesterday's visitors, but that he is adding 50 percent a week.