I hate to be a spoil sport, but when you reserve a table for 4 to 6 without any idea that others will be joining you it will keep others from reserving a table. I don't think that was the intention of the reservation system. If you remember, when we use to reserve on the first day of the cruise, we had to specify the suite numbers of the others in a large party. That would be their reservation, too and keep people from double booking ("I'll go on your reservation, then you can come on mine!"). The old system was much less convient but if the new system is exploited we may be returning to the old way because the fairness of the system was more transparent.
David