Shortly after I posted Github is my resume the responses started coming in. They seemed to fill these categories:
"Github is a portfolio, not a resume!"
I think this is rather valid, being a much more accurate description of the role that Github and other social coding sites are having in getting developer jobs these days. Two of the more choice responses in this category were posts by Gini Trapini and Andy Lester.
"In X years of hiring, I've never requested source code along with the resume!"
This comment raised the issue that personality, location, writing skills, etc were important. I agree that being able to not annoy your team into losing productivity is important, but it doesn't negate the frequent desire to be able to review the work of potential hires. Ignore the code at your own risk.
"Using only binary for calculations, how many ping pong balls fit in your car?"
A couple people said they prefer to ask programming questions or challenging problems in interviews to seeing portfolios of code. Personally, I think a few programming questions are okay but in my opinion 'challenging problems' all too often means sticking your interviewees with puzzles and trick questions that all too often have nothing to do with the day-to-day work of being a developer.