Those numbers certainly show how Facebook has sucked the wind out of MySpace. On the other hand, Friendster, Orkut, and others are still showing good year-to-year growth. Presumably, some of this is because of penetration in specific countries/regions.
Orkut rocks in India as that is the simple most of all. In India we have two communities Orkut and Chirkut.
I get a lot of searches for Chirkut for this definition of Chirkut "Chirkut is non-dictionary hindi word often used in Utter Pradesh and Bihar (two states from India) to praise a person for being loser, stupid and dullard".
Now I see most of my friends have started using facebook. Facebook is going hot. Also linkedin.
Orkut is weird, its number 11 most popular site on the web, yet no of no-one who uses it.
Seb7, MSN and Live are #4 and 5 most used sites, yet I personally know of noone who's using them either. :)
Probably both are in too thechie circles. MSN Messenger is by far the longer community* in the world and the Hotmail accounts outranks any other service in the web.
Maybe you don't use it or don't like it but people does.
* A community is a hub where you can find people, talk, and exchange things. Isn't?
It's interesting how different areas adopt quite different "standards" - it's the network effect at work. If you think Social Network A has better features, but all your friends are signing up with Social Network B, you will almost certainly end up choosing B instead of trying to be a missionary for A.