How big is too big?

I myself have started to lean more toward the smaller races.  Last year I ran the RNR 1/2 in VA Beach and just got sick of all the people.  I thougth it was overpriced and I was paying more for the name/race organization more than anything else.  Apparently they ran out of wet towels at the finish and were re-using the ones that had been thrown down- how awful is that?  I didn't even want to fight my way to post race food tent so I skipped out on the food.  I think for larger events you have to definitely be more patient and not expect things to run as smoothly and be prepared for anything to happen.

I've found that there are some really good smaller races to run.  I ran the Flying Pig Marathon back in May and it was awesome- had wonderful crowd support and aid stations every mile that were fully stocked.  It was well organized- I couldn't have asked for a better race.  Next month I'm running the Richmond Marathon.  It's a smaller race, but the entry fee is extremely reasonable (as was the Pig) and I've heard good things about it.  There's so many smaller races out there that seem to offer more with a cheaper registration fee.  I am really liking the smaller races so far!  I like to stick to races around 3,000 runners- definitely not more than 5,000.

Yes, the numbers in a tri don't come close to the numbers in even a medium sized running race.  My biggest AG experience in a tri was around 300 people.  In Boston I started with around 10,000 other people in the first wave.  Another 10,000 in the second a half hour later.  We did not have any real clear running room to set your own pace until well into the second mile.

I think that in a tri the more you have the worse it gets on the bike.  You can have a washing machine with only 200 people on the swim, at least for a little while.  But 2,000 people on the same bike course, especially if it is a multiple lap course, leads to issues.

For a seeded running race if you are really concerned about getting stuck behind slower people, then it is your own obligation and need to qualify to get into a faster corral to avoid the "masses."

The smaller, the better.

Some venues just can't handle large crowds.  City streets get narrow (at least here in Philly they do), which causes unavoidable issues.  If you're talking a trail run, then crowd size is DEFINITELY an issue.

I've done a few races recently where the crowd was not conducive to a good race.  I read the comment about starting further up.  This plan does not always work, as there is a corral system in place.  Additionally, when everyone is trying to start closer to the start, it tends to screw things up.