I'm in agreement for sure, though you don't need to already be registered to see and click the subscribe button currently. I just logged out to double check.
Right now, if I'm unregistered and I click the subscribe button, Tapastic offers me a few different ways that I can register for an account -- Facebook/social media being one of them. So there is definitely some API between Tapastic and Facebook to make it easy to register. I've converted some folks this way -- they clicked on the link to one of my comics, then they clicked on register, then they clicked on "register via Facebook". Then they keep up on Tapastic and end up finding other comics that they like too.
I'm just wondering/wishing if/that there was a way to skip the middle step and take folks straight to the "register+subscribe" page. I think that I'd get more conversion, and ultimately Tapastic probably would too, I'd think.