Are there any good reasons why a developer would buy a Chromebook over some other laptop, unless they are developing for the Chromebook itself?
Most of the time, I'm either at home or at work, so I just remote log into my development systems. I, personally, don't really need to lug around my entire development environment, though I used to be in that school of thought.
So, given that I really just need SSH, a decent Chromebook is cheap (as others mentioned), and can have a decent keyboard with long battery life. The one I have is around 1kg, so it is very "handy", and I carry it everywhere, as I would have a notepad in earlier days.