I have done 4 organized rides last year ranging in size from about 300 riders to 12,000 at the Hotter'N Hell Hundred in August. I really like doing them partly because paying for a ride commits me to keep training. If I pay my $30 to do the 50 mile ride, I am less likely to get lazy and skip working out. I also like getting to see new areas with the "security" of a planned route, rest stops and SAG support. Nearly all of my rides are solo with the exception of events so its nice to ride with others.