Note that I have also never done this myself, I'm just interested in the logic. I've read the arguments, and I'm just not understanding it.
To clarify, I'm talking about races that don't have a limited entry, do not require qualifying times and with the assumption you take nothing from the course. It is also assumed that you are either not crowding the course or you run on the sidewalk/offroad along the actual course. I'm also assuming you don't try to sue the race directors
Which brings us to the liability argument, a common argument made, which only points to a flawed legal system that needs desperately to be changed. It is incredibly retarded that judges have set precedents for people who don't take responsibility for their own actions to get millions in settlements, thereby increasing the cost of everything for normal people because every businesses and organizations are forced to protect themselves from these insane lawsuits and those costs get passed down to us.
The other main argument I hear is how expensive it is for race directors. I have a buddy who actually helps organize all these events for the city. He knows how much these road closures/cops cost. These races make a killing. I can tell you right now that a run with 5000 entrants will pull in about 200k in pure profit for a single race. I challenge anyone to post some numbers if you think these race directors are barely scraping by.
The last argument being that if everyone did it, there would be no more races. This argument misses the mark. Look at online media piracy. Anyone can download shows/music/movies for free.....so why do people pay? They pay because it's super cheap, or because they can offer something the free stuff doesn't have (convenience, better quality, etc). These same basic economic principles would apply to any race.
I think it just comes down to uptight people getting mad that rules are being broken.