The more the merrier!
I've had 10 people on my C-22 for a cruise on a local lake in 10-15 kt winds. The boat had no problem with it but as Keith said in an earlier post it is the sheer volume of people that might be problem. My 10 were familiar with the boat and knew how to stay out of the way and out of harm's way. I wouldn't have taken that many if there had been small children, non-swimmers, or people who were novices and likely to get hurt. Also, the water we sail in is 75 degrees in summer and I know from experience that the water in Maine is a whole lot colder than that, taking away some of the safety margin in case something goes wrong. I'd probably not do what I did on a lake in the ocean!!! In my case we had people all over the boat, 5 in the cockpit and 5 strung out over the foredeck and cabin top. I prefer to not sail with more than 4 or 5 others and the best sails are with 3 or4 people total.