Sounds like a great opportunity for someone to create a new coffee shop chain specifically centered around the idea of seating people with laptops for a long time. Actually I'm not sure why this hasn't happened yet.
$60-80 coffee per 4 hours - x * $40 for four hours of a barista(s) - employee overhead - electricity - internet usage - business overhead - rent = < $0
Rent is the limiting factor in this model, you want to be in a high traffic area to get those customers but not have to pay ridiculous rent and still have a decently sized store. Not going to happen.
A) people will just go to the multitude of coffee houses that still offer unlimited WiFi
And
B) you're no longer a coffee house, you're an Internet cafe / temporary office space offering coffee. Big difference.
It seems like there is a middle ground which has not been explored, which is simply a more expensive coffee shop with more space, where you are allowed/expected to stay for long periods of time. I would pay for that.
You can call that an internet cafe if you want, but it wouldn't really be like any I've been to.
Source: http://pulitzercenter.org/reporting/japan-disposable-workers...