They are a LOT stricter about ID than they were 5 years ago - 9/11 changed all that. When booking this tour you are informed that ID is <b>mandatory</b> for ALL attendee's, so in answer to the comment about 'who brings a birth certificate to an amusement park'...well in short, anyone who has booked the tour and doesn't have ID should!
I've done two backstage tours, the 1st I was asked for ID and the 2nd time I wasn't...however for the 2nd one we were the last to arrive in our group, I walked up and said "where do I check-in for the tour?" she said, "who are you?" I gave her names and she specifically said "well, as you're the last and as you obviously know your names I don't think I need to check your ID". So, it's not that she forgot, she just decided not to bother!
Now, if you want to take your chance that you'll get a CM from the 2nd scenario then by all means go ahead, but be aware that if you get CM from number 1 then you'll get caught out...and needless to say you'd then be treated as a no-show and you'll have just dropped around $50. And in case you think that wouldn't happen I <b>have</b> heard of someone reporting from these boards who left their ID in their room and was sent back from the MK to get it.
WDW has SO many different options on offer that can make a vacation that little bit extra special - personally I would just find an alternative to the KTTK tour...because if that messes up the memory would then prove to be a sour one rather than a nice one.