You should probably avoid wearing a helmet (or seatbelts in a car), because you never prepare/plan to crash.

Ok, got me. But a seatbelt and a helmet make me safer (IMO, anti helmet lurkers), shaving won't protect me from injury, only make it easier to treat.

During a commute? No. I don't plan on it.
During a cross race? Yes. In a mass start of 80 - 100 riders on a course that narrows in 200m from 15 riders across to 5 across on an off camber muddy downhill turn with a grass to loose gravel transition 3/4 of the way through I fully expect that at least 3 people ahead of me are going down and I might be part of that pile-up. Yes, I've practiced falling and perfected the tuck 'n' roll and the sitzplant (depending on the direction of the fall.
I am not good enough yet to be the internationally known master of the spectacular wipeout like Joey. (Who is OK) :lol:

... if it's road rash or chain ring lacerations, -then why not shave the arms too?

Personally, I think people do it because other people do it. The first couple of guys probably lost some sort of bet. They didn't want to feel like idiots so they started spouting off about aerodynamics, road rash and that it saved a few grams. That's all it took for the practice to catch on like wild fire.

Might as well weigh in on this dead horse. I used to shave about a bazillion years ago when I thought I was some kind of mountain bike racer. I did it because all the cool kids did it. It always felt weird but it made my legs look awesome, even with my super-pale Scots/Irish complexion. I gave it up after a couple years because it was just too much work and I stopped riding less often. When I got back into riding regularly again this year I considered it briefly. The wife didn't oppose the idea. I even asked the same question on here after reading a Bicycling magazine article on shaving this year. The take away is this:
1. Racers do it because they regularly get a massage after training and races and it's much easier to apply oils and embrocations on smooth skin. The same goes for sunscreen, however judging by how tanned most racers are, I don't think any of those guys are using it.
2. The side benefit of wound cleaning. Yeah, it's easier and band-aids don't hurt as much coming off smooth legs as they do on hairy ones. However, I don't really recall ever crashing and needing to clean up after having started shaving. I got more nasty cuts around my knees and ankles from the shaving then I ever got from riding related incidents.
3. Lots of guys do it because the other guys are doing it. It's a tribal thing.
4. Racer Dave Weins, known as, "The Vanilla Gorilla" (because he's big, blond, and doesn't shave - a bit like me actually), has been quoted as saying he doesn't shave because he thinks, "...it looks stupid." Incidentally, The Vanilla Gorilla wiped the trail with Lance Armstrong during a mountain bike endurance race. Just so you know, Weins isn't just idle talk.
5. Some other racer was once quoted as saying, in regards to shaving for wound cleaning - "If you're crashing a lot, you just plain suck."

I'm a hardcore commuter and rider and I don't shave. I'm proud to be a big, hairy, Fredly Vanilla Gorilla!

zombie thread, closing