I personally love twitter, because it is so easy to follow. I do not like that you can only type in a certain amount of characters on your tweets though.
Facebook is my absolute favorite though. It is easy to update with pictures, links, videos, and text. It is quick and painless to find friends. It is super easy to navigate and literally everyone is on facebook. Facebook has great Adverts that come up as users go to diffent areas of facebook...they are based on relevance to the indivitual facebook user as well...which is perfect for marketing to certain groups of people.
Myspace and Xanga were my favorite social networking sites before i got on face book...they do not have a lot of marketing though. They offer unlimited blogging space, and let you add your own background and change all text colors. Downsides--they are often frustratingly slow on computers that are not 2007 or newer.
As for yahoo, AIM or any other email bassed social marketing networks...i do not like them as well because they are mostly visable to users of that particular email carrier...whereas there are millions more users on facebook.
The other sites you referenced are all pretty obscure and unknown in the united states. For marketing I would go with sites like twitter and facebook because they are easy to use and almost everyone has one. They would probably direct a lot more people to your particular marketing area.