actually, better than pranking them (which lets them know you or someone else
is listening) is to just listen secretly so that you might be able to secretly
find out if one of the employess spit in your drink or not. (or did something
else to your food).

While the following item is not scanner related, it does have to do with this
thread and was reported in the newspapers and on tv here some time ago. I think
last year (2003).

A MCDonald's employee was spitting into customers' soft drinks (without the
customers' knowing) when and because the customers' ordered the soft drinks
with "no ice".

among doing other similar nasty stuff to the customers' drinks and food.

somehow, some customers found out and complained (several different customers.
A BUNCH of customers complained.

I think she was arrested (although I don't remember if she was arrested or not.
She was definitely fired though.

so now, I prefer to secretly listen rather than telling anyone anything.