shelleycat (who ended up deciding she didn't feel like coming along) had this idea that it would be less crowded than the Patricia Briggs signing we went to, since she figured a couple of webcomic authors would be less popular than a New York Times bestselling author. That's really kind of hard to say.
How many copies of a book does Patricia Briggs generally sell? 100k? More? Less? How many visitors does Penny Arcade get every day? 10k? 100k? A million? I really have no clue. And is there a difference in dedication between someone willing to shell out for a book and someone who visits a free website a couple times a week? Should that be considered in the "popularity score"?
There is one key difference as far as something like a book signing goes however. The key to being an "average" fan of an author is reading their books. The "hardcore" fans may find the author's website (or blog or forums or mailing list or whatever) and participate there, but that's a very small percentage of the total fans. The key to being an "average" fan of a webcomic is, well, reading the webcomic. Which means going to the webcomic web page. The "hardcore" fans in this case will still be the ones who delve a little deeper and participate in the forums and other communities centered around the web comic.
So this means that when the author announces a book signing tour the people who see it are the hardcore fans who regularly visit the web page/forums/whatever (along with the small segment of people such as shelleycat and i who just happen to see the sign while walking past our local bookstore.) When the web comic people announce a book signing tour they're going to put it on the web page that _every_ fan visits. If they also work it into the comic then pretty much everyone who could possibly care will know about it.
So the sessions was supposed to start at 7. I had a few other chores to do at the mall and got there about 6:40 or 6:45. I bought a copy of the new book, plus the other compilations i hadn't picked up already, and went up to the event area. The 50 or so seats were already filled up at that point, and people were starting to fill in the back. I was one of the last people to be able to stand in the area behind the seats, and after me people started backing up into the walkway between the shelves and the escalator atrium, so they could see the table Tycho and Gabe were going to be speaking at over the balcony. That "line" ended up wrapping up all the way past the atrium and around to where the escalators came up. At some point people started filling in the other side of the atrium, though that meant they were probably looking at Tycho and Gabe in profile. All in all there were well over 100 people there i think.
They started up pretty promptly at 7. They spent the first hour answering questions and then switched over to signing books. Even with being at the back of the seating area i was still easily in the first half of the line. I got the new book signed and my copy of their very first book (i offered to give it to burn as a sacrifice in an eldritch ritual of vengeance, but they said they'd gotten over their feelings about that =) and then hung around in the SF section until everyone else had gotten their stuff signed, which took until about 9 (an hour after they started the signing.) I then got back in line at the end so i could get the other three books signed, just cause i didn't want to be that guy and make them sign five things my first time through the line :)