Your comment reminded me of this short story that was posted to Slashdot a while back.
I really hope it's just patent protection. Its probably cheaper to patent something like this than to have someone else do it, and then pay your army of lawyers to fight off the lawsuit and get the patent overturned.
Serious Sam HD The Second Encounter also offers co-op and is mostly a run and gun game. It's a minimum of story, and a lot of blowing shit up. Not sure if the first encounter has co-op as well, I only have the second because it was on sale after a free weekend.
Just curious, when you log into the Verizon wireless website, under your data usage, does it list your monthly allowance as unlimited or as 5GB? After reading this story, I logged in to see what was listed, and for my Droid it has an unlimited cap.