It's just an awful category descriptor... that doesn't seem to stop people asking me about whether they should get one or not. Here's a pretty good overview of notebooks in the category.
If you live on the web, do a fair amount of TV surfing, and are looking for a notebook to chuck in your bag or have laying about the living room, they represent a pretty good choice. Damn cute as well.
I'd shoot for a Dell Mini 12. This one is way cool.