I don't think the level of gore would be anyone's answer of attracting a teen market, if they wanted to attract teens they would have thrown this into a modern setting and obviously cast it with a bunch of teens (actually 20-30 somethings that they pass off as teens).

Anyone that comes out of the theater only discussing the level of blood and guts is only there for blood and guts. People that go to see a good horror film, drama, good acting, great sets, atmosphere, etc. will (at least they should) come out talking about those things regardless of the gore level. A classic can exist with or without gore but without those other things, it'll never be a classic. I personally want to see all of those things and I want to see the blood, guts, bowels, bones, ripped flesh, etc.

I bet Rick never thought there'd be controversy over showing to much gore in a horror film, well maybe from censors but not from horror buffs!