I'd just like to chime in with the fact that Docker does throw a runtime warning on kernel versions lower than 3.8 [1].
We agree that a specific kernel dep for a newer kernel is awkward, but it's a fact of life and we'll take your advice, Ben. :)
For this reason, I've added "linux (>= 3.8~)" to our Recommends [2]. As for why Recommends instead of Depends, that'd be for several reasons. One of the most major is that then it works fine in a container, where we intentionally don't have any kernel installed, and also because the package "works" with lower kernels, but as far as upstream is concerned, you're on your own and get to keep whatever pieces that creates.
♥,