Webcomics have a long (by which I mean long for you guys, the seven or so years that webcomics have been a thing* haven't even been a sixth of my life) history of embracing social issues. I won't go into specifics, but I've seen a huge number of pushes both here and elsewhere for donations of money and time to every cause that has ever been a cause for anyone, ever.
Problem is, a surprising number of these causes are either meaningless or being handled in the best way they can be already. To give an example: UNiCeF, the Christian CHildren's Fund, and CARE for Children all address the social and economic conditions that give rise to most of the human trafficking problem in the third world. Hoever, these noble and noteworthy chairites have lost donors and attention lately, because Webcomics (and, admittedly, other media) have focused their energies specifically on one or two charities that promise to directly combat human trafficking.
This morning, I noticed a number of sites had big red ads advertising the dangers of the Stop Online Piracy Act and the Protection of Intellectual Property Act. And these were dangerous pieces of US legislation. Back in October, when they were introduced into committee. Now, they're unlikely to ever even reach the floor of Congress. Since then, the RIAA (one of the bills' major proponents) has been discredited as having any real authority in the moronic battle against piracy (RIAA computers were found to have multiple, illegally copied, seasons of the Showtime Series "Dexter") and major corporations that might have supported the bills (like Sony, Nintendo, and Microsoft) have either pulled their support or are actively opposing the legislation. Other companies that depend on user modification for their products' popularity (like EA and Oblvion) or just rely on "borrowed concepts" for their income (like Blizzard) are preparing banks of lawyers to challenge the laws if they somehow get magically passed. It's become a non-issue.
I'm not saying that these things aren't important, and I'd be the last one to say that if you feel a responsibility to engage your readers in the debate or support of important issues. That responsibility carries with it the further responsibility to ensure that you have done due diligence, that you have looked into the matter and know where your head is before you rush out and try to rally the troops.
Yes, you have a social responsibility, but if your comic is popular enough that you feel that responsibility, then you should be aware that you are holding the internet equivalent of a shotgun. You have a responsibility to ensure that it is properly aimed before you fire it off. Think of the worst depredations of Krahulik's temper or Anonymous's Groupthink and ask yourself if you really want to be responsible for that kind of damage.
*Yes, I know webcomic have been around since 1998 -- 1990 if you count one-shots on USENET and the networked Bulletin Board Systems, but they didn't really start attracting large numbers until about 2004-2005.
What I lack in sincerity, I make up for in sarcasm.