On Mon, 24 Mar 2008 10:54:19 -0700 (PDT), "Robert M. Gary"
wrote:

I'm not aware of any photo requirement in the US at this time.
However, if they did make it "optional" I could see a lot of airports
denying ramp access to pilots who did not opt in.

Given the current requirement for photo ID (which virtually all US
pilots possess) in addition to an airmans certificate to access the
ramp, it would be redundant (and hence needlessly costly).