We run sailboat races in HOLLYWOOD (private sim) using the TAKO sailboat (18 prims, scripted). The sailboat reads a wind setting device that provides much more realistic wind that SL wind.
For many months we have run regattas with an average of 5 to 6 boats in each race. However racing has become more popular and we are now getting 9 and 10 boats per race.
Up until an incident on Sunday time dilation issues were pretty much non-existent. On Sunday during the second race (10 boats) a large number of spectators were riding along as passengers during the race. Thus, for the most part, each boat of 18 prims carried two avatars (with typical numbers of attachments).
About half way through the race the sim slowed to a virtual halt (literally, hehehe). I checked stats and noted that time dilation was down to 0.04. The fleet was frozen in place, however we could CHAT. After about a minute of this condition I contacted a Linden. Coffee Linden came to our aid. He (she?) determined that it was the large number of avatars in a large number of vehicles all moving at the same time that cause the time dilation. Other than that, the sim had no problems according to Coffee. Dilation recovered a couple minutes later and the race was completed with no boats "disabled" by the incident.
I announced Coffee's analysis of the incident and all passengers retired to the local race viewing area for the next race. The next two races (still with 10 boats but with only the skippers aboard) ran smoothly with time dilations in the .90s (.98 or better for most of the race).
It appears to this non-technical soul that the presence of 10 or so additional avatars in motion with the 10 racing was clearly the cause of the incident. However I thought I would post the incident here for comment.