It sounds like some of you have some dangerously large group rides! 30+ people in one group is insane when there are still motor vehicles whizzing aroun you. The way that "large" group rides are done in my area is that everyone meets in one place and then split apart based on strength and goals. There may be 30-50 cyclists gathered in one place but everyone leaves in different groups rated on an "A" through "D" scale with 5-10 minutes between departures (faster groups leaving first). "A" generally meaning that the group is going to maintain a minimum of 21-22 mph average with no upper limit to the pace (been on a few "A" rides that have averaged close to 27mph when the local cat 1s and 2s feel like hammering! /img/vbsmilies/smilies/eek.gif), generally experienced cyclists and racers. Then each letter goes down to lower and lower paces with a typical "D" ride being around 12-14 mph average. This grading of pace generally means that each group is between 8 and 15 people, depending on how many people meet up before the beginning of the ride.
Structuring group rides this way also seems to help people progress fairly quickly in this area. For instance, a "C" paced rider who thinks he is getting too strong for his group can go out with the "B" group and, if it gets too hard for him, he can drop off the back and easy pedal until he is reunited with his old "C" friends. In this way it is not as intimidating for people to try to push themselves to progress and get faster since they know they won't be left for dead if they are dropped by one of the faster groups. Its just a matter of waiting for the next group to roll through. This structure also means that the faster groups don't need to worry about waiting for any dropped riders.
Structuring group rides this way also seems to help people progress fairly quickly in this area. For instance, a "C" paced rider who thinks he is getting too strong for his group can go out with the "B" group and, if it gets too hard for him, he can drop off the back and easy pedal until he is reunited with his old "C" friends. In this way it is not as intimidating for people to try to push themselves to progress and get faster since they know they won't be left for dead if they are dropped by one of the faster groups. Its just a matter of waiting for the next group to roll through. This structure also means that the faster groups don't need to worry about waiting for any dropped riders.