My reasons for saying less Hetalia and Homestuck is for three main reasons:
1) The way in which these various panels are run are the same, with insignificant differences. There are plenty of other ideas that are worth having that get denied for the same reason, yet these fandoms are allowed to have multiple panels. (Though I did appreciate the idea of having a "Let's get along" panel between the two fandoms; some of their members need to chill).
2) With less of these two types of panels occurring, there's more room for a wider variety of panels. There's some talk about doing more panels that relate to Japanese culture some how. (I'm thinking about covering some of Japan's top holidays and their references in anime titles). These seem more "anime con" relevant than a webcomic or a single series, so I'd like to see less of them in order to make more room for these.
3) I'm not sure about the Homestuck crowd, but from what I've seen and heard from the Hetalians, a big reason (but not sole reason) for multiple panels has been because many of the fans want to do their own spin on things or they are having squabbles with their fellow fans. I may love certain shows over the rest, but not enough to go "Fine! I'll run my own Ranma 1/2 panel, and it will be better than what they're doing!" In an indirect way, it feels like the programming department is pandering to their childish drama-fests that I find to be anti-con-like.
I don't care if there is a panel for each fandom. However, two of each is pushing it, and three or more of each is insane, especially if at least two of them are the same thing but run by different panelists. Other fandoms and ideas ought to be given some time, too; having the same restrictions on them that every other group has to abide by is only fair.
Slight note for you, prussia: I've actually ran at least one panel every year since '08. With that, I've also had some ideas shot down, sometimes for the reasons that I've brought up. (Others have had different reasons, too). Not every idea gets approved; as I understand it, most submissions get shot down, and for various reasons. Just submitting something doesn't guarantee that it will happen.
Oh, something else for Paladin's original question: in the event that panels (or events) require lines, it would be nice if the Yojimbo that are watching the door know what they're doing and aren't jerks about it. I know that a lot of the previous year's problems are going to be addressed for '13, but some of the issues shouldn't have even been issues to begin with. Hopefully they'll be better this year...