It is OK. Road racing today caters to the penguin masses in order to fund a bunch of non-American runners (if you are any type of legal citizen or contributing to the economic strength of your given region of residence in the US through work and expenditures of your profits I consider you to be an American) who take the money Americans put up in race fees and bring it back to their homeland to fund their contrymen/our competitors! So you as John Q. Taxpayer who is paying through the nose to live in America and decides to ghost run a race a couple of times should not feel bad.
I have only done this once at TCM, using the race as a training run (17 miles) to pace a buddy up a gradual hill by UST. I dropped out two miles before the finish and did not partake in any of the post race goodies, drinks on the course, or use a port-a-potty afterwards.
Here are some guidelines:
1) dont dare take postrace food
2) dont do this regularily
3) pull out of the race no closer than 400m from the chute
and
4) dont be a jerk and start in the first few rows of a major race (200 or more +)
The Bottom Line is that if you are a dirt poor person then go for it but sparingly. Even I do not have respect for people who can ghost run a race yet afford to buy their buddies beers after the race. Ghost Racing is only okay if your economic need necessitates it and/or you are helping a friend through a race.