So, is it common practice? Should we encourage each other to do this? Does Github mind? Do they have an official policy stated?
Linking to GitHub "raw" files has some issues as outlined by Dave Ward's answer.
I suggest you look into GitHub Pages as an option.
This was recently asked in github's support forums, and the official answer was that it's ok.
Having said that, I agree with other answers: github was never really meant to be a CDN, while Google and Microsoft have specific infrastructure for that.
It's fine for prototyping / personal stuff, but for production I would look at:
http://cachedcommons.org/ -- no longer available
I'm doing it for months now, had some concerns first but it's totally cool if you have no problems with your files being publicly available, use minified versions if you care.
But still - Google & MS rule the space for jQuery & jQuery Templates - so I use them for that.
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