I disagree with the notion that crashing makes you more experienced at riding beyond giving you insight as to the consequences of what NOT to do, or how you SHOULD react to a situation.
I think not crashing is a sign of luck and riding within your limits, definately a mixture of the two.
Major milestones for me have been:
1) Getting edumacated with MSF, books, and reading posts
2) Getting on the highway and feeling like I was going to blow off the bike and die at any moment
3) Feeling capable at operating the bike in all types of traffic and weather situations
4) Reacting to unforseen/preventable situations, e.g. evasive manuvers
5) Reacting to unforseen/self-induced situations, e.g. wrong apex or entry speed
6) Getting on a racetrack and being lapped by 125cc bikes
7) Looping a 49cc scooter due to a wheelie gone awry
12k miles and 0 'motorcycle' crashes later, I feel "less new" and somewhat suprised I haven't crashed yet. I am sure the day will come, but until then I say worry less about crashing and more about NOT crashing.
The only thing I learned from crashing the scooter was that if you don't respect a machine it will kick your ass with all 49cc's
