I noticed that recently, how tablets have gotten much bigger (12-13") and detachable keyboards are now the norm, I'm seeing them everywhere. It makes me laugh to think that the killer feature a tablet can have... Is a keyboard! I feel like we've sort of come back full circle. Netbooks were getting popular before tablets, because people had a need for a computing device that was more portable than traditional laptops.
A Microsoft Surface, or a big iPad with a keyboard, those things are basically, like you said, thin and light laptops.
Convertible tablets like Microsoft Surface don't count -- those are laptops with detachable keyboards.