I need to see some identification...

I went to Wal-Mart today, I really wanted to buy The Hangover. After I got it off the shelf, I walked to the front of the store, and hoping that I wouldn't get carded for the R-rated movie, I went in the self-checkout. But as I stood there, ready to pay, some woman, hardly older than myself comes up to me and asks to see my ID. I gave it to her and she checked for the date of birth that the screen told her I needed. She just stares at the screen for about 15 seconds, obviously debating on whether or not to let me make the purchase anyways. She then told me, "I can't let you buy this", and just walked away. Needless to say, I was frustrated, so I went to my house and watched Superbad instead. It just wasn't the same.