It's not a bad approach, but I wonder if the talks oriented toward novices who may be new to Python/Django or programming in general are willing to sign up for a GitHub account (or even know what it is) to vote. Maybe this should be taken into consideration as these vote totals will probably trend lower than other talks.

Really? Is there a test? What if I like Mecurial and use BitBucket? Does everything have to be based/hosted on Github?

I use Bitbucket too, but get over it, it's just a poll, not that this breaks your workflow or prevents you from using tools or anything. It's a throwaway use case.