I love Github, but I certainly must agree with point number 1. I work as a CTO at a start-up here in SF full-time (which means, 8am-2am). We have to a lot of developers and designers around the world which means when I'm not coding, chances are I'm managing. This leaves me very little time to contribute to my own personal projects, much less open source projects.

I'd say that using Github as a resume is a great idea for Jr. Developers and students looking to get some "cred" in the real world. But that really just refers back to knowing your industry and being professional about your work.