The Hyphenator
Draftee
Officially, yes they will be checking AFL membership cards (and IDs):
'To enter the stadium on the day of the match, you will require:
>> Your Ticketek ticket to scan for entry into the ground
>> Your 2012 AFL Membership card to verify your membership
>> And photo identification to verify that the membership is yours'
http://aflmembership.com.au/match-information/grand-final/
My understanding is that they can't realistically check everyone entering the AFL members reserve - I'm pretty sure I remember reading a thread on this on the main board...
As Bedford said, if you get caught trying to enter without a membership card, both you (no entry to the game) and the person whose membership was actually used to purchase the ticket (possibly loss of membership) suffer. Risky strategy.