"At a fine-dining restaurant, nobody should expect to be seated with an incomplete party, ever." [Boston portion: http://chowhound.chow.com/topics/774561]
On this point I most heartily disagree. The finest and fanciest restaurant at which I have ever eaten is Gordon Ramsay's Royal Hospital Road in London. Back then it had three Michelin stars, if my memory is correct. I came there at the proper time to meet a foodie friend for lunch. He called the restaurant to give me the message that he was delayed in London traffic. At that point the maitre de asked me if I prefer to continue sitting in the lounge or would like to be seated at our table.
That should be what all restaurants, plain or fancy, do. I reject the practice of delaying the sitting until all have arrived.
Now at GR's RHR waiting for a table was hardly an inconvenience. The lounge had comfortable seats and I could have ordered a drink while waiting. At most restos the holding area is not as comfortable, which makes the wait all the more annoying. It strikes me as the most elementary principle of service in the so-called hospitality industry that you do not keep someone standing in an uncomfortable area if you have a seat in which to put them. There may be some rationale for delaying taking the order until all have arrived, but there is no reason not to seat one's guests as promptly as possible.