Don't you just feel like an invisible speck when you walk up to the checkout stand of a store and the clerk is talking to a co-worker, and he/she doesn't even acknowledge that you're there? He/she just starts scanning your items, stops talking just long enough to say "$31.55" and put his/her hand out for the money or card? 

Didn't these people's parents ever teach them any manners? Didn't their bosses? Worse yet is when the two co-workers are cackling over some stupid joke.... or gossiping about another co-worker... and worse YET, poking fun at the previous customer!