Twitter topples MySpace as third-most popular social networking site. (What took so long?)

Finally, MySpace is knocked down a notch. The former heavyweight social networking champion, who fell hard from glory in the wake of Facebook and others, has been bumped from third to fourth place (based on internet traffic). 

Twitter is nearing 100 million monthly unique visitors, up a staggering 76% from the same time last year. MySpace, on the other hand, dropped a painful 17%. Facebook came just virtual inches from a stunning 600 million unique visitors, a growth rate below Twitter’s, but still jaw-dropping at 54%.

Wait, you ask now. Who’s number two?

Well, arguably not a comparable social networking site, but the second-place slot is filled by Microsoft’s Window Live (140 million unique monthly visitors). Not much to say here, really. It’s a boring place to network and socialize, but it’s buoyed by the Windows Live email and Messenger platforms.

Though, I guess if I’m not wanting to counting Windows Live profiles as social networking, I should take into account the fact that Twitter emphasizes it is not a social network either. Co-Founder Evan Williams calls it a “real-time information network.” Let’s shorten, shall we? RT InfoNet, maybe? Or… how about social network? D’oh.

It will be interesting to see how Twitter’s 160 million users respond to its “New Twitter,” a very thorough redesign of its classic platform. Unlike Facebook’s many facelifts, the Twitter redesign is a logical and sophisticated evolution that doesn’t just move everything around randomly. If its perceived well, Twitter could maintain its incredible growth rate, and will be a serious contender for second place this time next year.

MySpace, on the other hand? It’s still buoyed by the relatively untapped market of networking for musical artists, but the tacky, juvenile ambiance it tortures users with, and the slew of superior competitors, will mean MySpace is on the decline to death.