Huffing paint and passing counterfeit bills

I was in Home Depot over the weekend- part of wild errands-running event - and I needed to buy a utility knife, some electrical tape, and a can of spray paint. I went to the self checkout since I only had three items and there was no line there. Utility knife, no problem. Electrical tape, also no problem. Spray paint - problem.

The self-checkout stopped and flashed a message that a cashier would need to over-ride. I turned and the cashier for the area said/asked - with a chuckle - "You're over 18, right?"

I'm guessing he was commenting on my gray hair and bald spot.

I told him I was and apparently I had enough venom in my voice that he quickly followed up with "As of last week, right?"

Another chuckle. I shared this one with him while I completed my transaction and planned his death. I also got $20 cash back which will be significant later on.

As I understand it, the check he did was to prevent some kid from buying spray paint and then huffing it. Questions:

1. Are 18 year olds suddenly smart enough to not huff paint?

2. Are they responsible enough to keep the paint away from kids who might huff it?
3. I may have watched too much CSINCISSUV, but isn't the electrical tape and utility knife more suspicious?

I headed on my way and at my next stop, I paid cash - using the $20 I had just gotten from Home Depot. The clerk behind the counter used a highlighter to test the bill and make sure it wasn't counterfeit. More questions.

1. Are the staff at Walmart trained by the Secret Service or the Treasury Department to detect fake bills with the magic highlighter?

2. What, exactly, would have happened if the bill had been fake?

3. Granted, this is the kind of place where someone would try to pass fake bills made on a black and white copy machine - but seriously, a $20? I could see if someone threw out a $100 to buy a pack of gum, but what's next? A set of scales to measure coins to make sure they aren't fake?

Makes me glad I wasn't trying to buy cold medicine or board a plane as the pilot.

Whatever happened to the "innocent until proven guilty"? Two cases - in less than an hour - where it was assumed that an everyday process was a criminal act.

(insert head shaking here)

Same reason the terror alert is always orange - fear and control.

Okay, down off my soap box before I get myself worked up into a lather. I gotta get back to work anyway.