Augie de Blieck over at CBR has a summary of the problems with mainstream comics publishing that's pretty accurate. He highlights the word "purposefully" a couple of times and though it's a bit hard to picture editors or marketing staff at The Big Two consciously limiting their audience it may be just as hard to think that they're completely unaware that this is exactly what they're doing. High prices, convoluted stories that lose even readers like me, dedication to a format only fans like, etc probably drive away readers just as much as any nerdish aura to comics. Just remember a few years ago when it looked like the entry of trade paperbacks into mainstream stores would be the breakthrough? Just walk into a big store now. If you can even find the things (and Borders seems to shift them periodically) there's no concession made for readers. Some tpb series are numbered, some aren't, and in any case which series needs to be read in order? If somebody likes the Iron Man movies and goes into the store how do they know what to do with a couple dozen books? (Hint: Don't start with the "Essential" volume 1 which of course sounds like the most obvious.) The Big Two increasingly put new releases into hardcover first apparently to satisfy a fairly small slice of their already small fan base but apparently also to seem like "real" publishers. Thing is that unlike a regular trade publisher they've already recouped costs through the original serial publication so the hardcovers are bad marketing excesses. You have to wonder when even a newish publisher like Boom follows this same pattern for their Pixar and Muppet books - who on earth buys the pamphlets for The Incredibles or Muppets other than collectors? Just starting with the tpb is going to hit the parents as well as the regular fans.
And of course this doesn't even get into the managa world which is in the start of its long-anticipated contraction.