I agree, but I suspect most of them went through a traditional publisher. The big difference with what we're doing is that breadpig inverts the profit structure -- the artist (that is, xkcd) receives a majority of the profits from the book. We're aiming to deliver a high quality product similar to what you'd get from a 'traditional publisher' (we're using their suppliers for paper, printing, etc.) but properly rewarding the people creating the value.

Admittedly, one of the ways we've done this is by mitigating the risk that usually comes with publishing a book (surprisingly, to me at least, as risky and blockbuster-dependent as a Hollywood film) -- xkcd's readers know that merch (and this is one extension of it) is what pays the bills. And there's plenty of them, hopefully more than a few will want this on their bookshelf beside their old Calvin&Hobbes collection (I know I do, that's why I wanted to help this come to fruition).

Other websites that became books:

I Can Has Cheezburger?, Garfield Minus Garfield, Hot Chicks With Douchebags, Suck.com, Indexed, Sleeveface, Passive Aggressive Notes, REAL Ultimate Power

http://www.avclub.com/articles/why-buy-the-cow-27-popular-we...

don't forget PBF: http://www.amazon.com/Perry-Bible-Fellowship-Almanack/dp/159...

Another well known webcomic which has been released in print form is Megatokyo. In fact, they're up to five volumes now! See: http://www.megagear.com/category_s/67.htm