Unfortunately, becoming uncomfortable is only part of the problem with a foam futon Mattress. Go wander through a foam factory for a half-hour or so and it won't take long for you to realize there are some nasty chemicals involved in the production of foam. Of course this industry has been forced to make some changes in the chemicals they've used over the years (as the hole in our ozone continued to grow!), but that doesn't mean that this billion-dollar industry just rolled over like a puppy and became "green." (That's what lobbyists are for, right?) Frankly, with today's technology that isn't really possible. But generally, if you're sticking a product in a box with a couple of custom foam end-caps to protect it while it ships, this isn't really that big of a problem.
However . . . does that mean that you're can safely spend every night sleeping on foam? Take a little time doing a Google search for the terms "off-gassing" or "out gassing" as it is also called and you will quickly began to see that poly foam as a bedding choice is not a good idea.