Apparently now in Hoboken you need to ask if your waiter is actually employed by the restaurant

Yes food fans, a new kind of scam is afoot in Hoboken. Twice a man pretending to be wait staff at two local restaurants approached tables of patrons and asked if they "Were ready to pay". After collecting the cash for the bill, he beat a hasty retreat right up and out of the establishment. Hobson's Choice, at 77 Hudson St. and Margherita's Pizza and Cafe, at 740 Washington St. were both hit with this scam. The man was described as being 20 something and having spikey hair. In the Margherita's case he asked to be put on a waiting list for a table and sat and it appears waited for a table ready to pay with cash and jumped into action.

In both cases the restaurants did the right thing and waived the bills as they said it wouldn't have been right to charge their customers twice.

Well here's something else to be wary of diners. We're not sure there's a polite way to ask your waiter "Are you SURE you work here", but maybe it's time to start.