One major flaw: it assumes anyone you would want to hire uses Github, as opposed to Bitbucket, Gitorious, Google Code, Launchpad, the numerous other code hosts I missed, or hosting their code on their own server.

And if Github becomes "the standard" for hosting software such that everyone looks for code and coders on Github instead of other places, that would be detrimental to the FOSS community as a whole - not only in Github's lack of competition with other code hosts, but also in git's lack of competition with other VCSes.