This is the first time I've heard about Foreman, and it looks like it could be very convenient for development. I appreciate the attempt to abstract from process requirement details in the same way that Gemfiles do for gems. I think there's the germ of a good idea here.

The example for a production environment, however, is pretty unpersuasive. Tools like Passenger (mod_rails) dynamically start and stop processes depending on load, number of requests, etc. That is much more useful than just saying "start four mongrels".