I have seen something along the lines of "parties of 8 or more will have a 25% gratuity added to the check" on menus in many US restaurants. Its been on menus for as long as I can remember. I assume its legal if it is visible, as it is virtually no different than listing the cost of the food - it just requires more mental math. However, that doesnt make it so, so I was curious. Is this legal? What if you didnt read that part of the menu? Can you be expected to read the entire menu?
I went to lunch by myself today (in Virginia) and I was shocked to find a 20% gratuity already added to my check. It was not written on the menu, nor was I told about it. I have been to this restaurant dozens of times previously, but this was the first time in ~6 months. When I asked the waitress, she said there was a sign at the front of the restaurant. I went to the front and there was no sign. I asked for the manager, who (of course) said it was legal and the waitress should have told me (she didnt). He went to look for the sign, but it was not there. He found it behind the cashier's counter (as in someone took it down and it was not displayed). He offered to take the gratuity off, to which I said no. I normally tip 15% for normal service, 20% for good. so I wasnt going to argue over a change.
On a side note/rant, charging almost 2x the cost of a 2 liter bottle of soda for a glass of soda should be illegal :P