I have a theory that I believe to be true, but I do not have the real need to research and prove if it is true or not. My theory is that there are only 100,000 comic fans left in the USA. I know some books have print runs of over 100,000 - but very few and one month recently not a single DC book had orders for over 100,000.
First let me define comic fan. That is a person who reads new comics and makes said purchases at least once a month and reads at lest 3-4 titles a month. So my true fan only has to outlay less then $10 a month to qualify (need a heavy burden).
A successful book can sell 20,000 copies a month and still survive in today's market (and if the price point is four dollars I think it can survive in the 10,000 or less range).
Now my central premise is that at least half of us have a blog or webpage of some sort that identifies us as comic fans. There are over 16,100 people on My Comic Space and then look at every blog that is on comics and follow the links and then follow the links and you will discovered that we have a huge community of bloggers. I'm willing to bet that between comic websites such as Comic Book Resources, Newsarama and such, Comic Store Websites, creator blogs and their websites and message boards, comic book dealers on E-Bay and actual blogs (such as mine) that 50% of the community is espousing or soliciting the other 50% to buy something from them.
As I don't necessarily surf around on other subject matters as extensively, my theory is all conjecture, but I bet as a group more of us are online that almost any other group or interest. We are predisposed for the internet as many of us enjoy new things and reading - so the internet was a god send for us. Finally for the most part we all had to enjoy our habit in relative solitude because the people at your work place or other gathering places did not want to talk comics like they would a shared experience of news, movies or TV.
Just my view.