All very good points, thanks for the answers guys! I also wanted to say, i think the decline in younger readers may also have to do with the "Image" associated with comic book readers/collectors. To the general populace if you read comics, and know all about them, you are considered a "geek". People see those guys at comic-con in those odd costumes, and doing really weird things. To people those guys in those costumes at comic-con is what people think all the comic book readers are like. Most pre-teens and some teens never pick up a comic, only becasue they think doing so would put them in the same image as the trekkies and other "geek" fanbases. They don't want to be a "geek", and so even of they do read comics they would never tell their "buddies".
Today "fanboys" even make fun of other fanboys online all the time. Kids these days, and people in general try so hard to fit in. Apprently takeing time to read a 32 page picture filled story is "un cool". They don't want to be the guy that collects spider-man comics. I know from personal experience, as i still haven't told my friends i read comics. I am black buy the way, and the young black people i hang out with, are into hiphop and "Thug life". A guy who reads comics to my friends is loser. So maybe its not just the mature titles these days, maybe its just the bad image people have of comic book readers in the media.