Boy oh boy, I come back to FFA and see this thread got to 2 pages and I'm dreading reading it, and hey, most of the new posts since I've last looked aren't even about me or the situation, so it's whatevs.
It's not just nabs that I've heard women don't want to be hit on at work from. I've read that on the net from women too. Though like you allude to, it could depend on the guy's charisma, confidence, etc. Anyway, my way of thinking was if women don't want to be bothered with being hit on and having to politely worm their way out of a conversation they don't want to have while they're working, the situation I presented in the OP allows me to express interest, but also in my mind, not really bother her. There's no conversation to worm her way out of, I'd just hand her the receipt and leave, and by the time she realizes what I handed her the encounter's already over. If she doesn't want to deal with me, she doesn't have to, because I already left.
It would take a LOT of practice of just making light small talk and nothing more with CSR's for me to get anywhere near comfortable enough to ask one out in a more traditional way.
I've definitely thought about looking for women to ask out at concerts, but most of the women that catch my eye are there with a dude, lol. Another roadblock to this is most of the concerts I go to are out of town (usually San Francisco, L.A., or Las Vegas), and I have no interest in traveling long distances to see a chick I just met. But then again I guess at those out of town concerts it could be good practice for me to just try talking to them without trying to hookup.