how'd you folks know i was gonna chime in....
yup

never had to show one and in fact, where i am "technically disabled" as i don't have to ever wear dress shoes again as i need walking shoes for the support, the minute i "get the note", i have to declare on everything and anything that i am disabled and that's something i prefer not to do

i do wear "walking shoes" since my ankle surgery. black brown & white with big (and i do mean big) thick soles. when told (yes, told) to remove my shoes, i simple tell the gatekeeper that i am wearing orthotics. only once have i had to give the definition of orthotics tho on several occasions, have i had to describe what they were made of ^. i do not alarm and take my secondary "with no alarm" (shoe swab and sometimes hand swipe) but have had to remind the gatekeeper on a few occasions to tell the screener that i did not alarm.

i have been asked if i can take my shoes off while sitting so they can be x-rayed ("cutesy" screener tactic to pump info out of me) and i simply say "no, i cannot take my shoes off my shoes and/or stand and/or or walk without great difficuclty (the truth) and that usually solves the issue.

however on one occasion i did have to pull this out of my bag (see page 3): http://www.tsa.gov/assets/pdf/special_needs_memo.pdf. actually had the supervisor take it out (in the presence of the screener and a cop [my request as it was getting ugly]) as remember we can't touch our bags during the screening process as we all have to good sheep howver the tsa memo put and end to the foolishness in about 6 seconds.

n.b. the tsa website is a problem child w/safari so use firefox