I've been lucky because my sense of self-preservation is too strong
The first time I crashed was into someone: I was heading home from my local train station after my first bocking meet (okay, it was just 2 of us) in Manchester in the summer of 2008 a few weeks before Capital Bocking 08. There's a road that goes downhill from my station then around the corner, and on this hill is a bus-stop.
Bocking down a hill doesn't seem that bad, but I was carrying my empty stilt bag on my back, using the grip-straps as shoulder straps (nothing wrong with that, but it did throw my balance off a bit), factor in the fact my legs were already kinda tired from the day anyway meant I promptly collapsed into the arms of a hapless soul who was standing at the stop (fortunately he was the only one too). It wasn't a proper "fall" as my knees never touched the floor, I just collapsed into his chest and he helped me get back up. I apologised most profusely and excused myself "I'm new to this", he muttered something about it "being alright" and I was on my way, stepping down the road and around the corner. I don't think too many people saw.
After that I was more-or-less alright, my fear of falling has stopped me from pushing myself into doing tricks that actually impress people.
The next time I fell was about 9 months later just after the end of the academic term (June 2009), I had some postal-rent DVDs I needed to return so I thought I'd bock down to my halls of residence's reception (in another building, about 250m from my block), but my blood-sugar and energy were really low; I got off to a good start and picked up some speed as I went round my hall's block but as I approached the access road I started to lose control over my legs and I just wanted to crash as soon as I could, but I didn't want to land on the concrete I was standing on. Along the path was another guy, I overtook him before promptly feeling totally exhausted and I aimed directly for a flowerbed a few metres in front of him, I lent over to my right and fell onto my forearm and landing on my back with a small thud, I was winded pretty bad. That was my first proper fall. The guy I overtook gingerly walked towards me and I just dismissed him "I'm *gasp* oka *cough*aayy!", he asked me if I made my stilts myself "No, Internet!" and he 'hmphed' and walked off. I later overtook him again, this time on foot, carrying my stilts under my arms and totally out of breath. I don't want to imagine what he thinks of me.
And whilst we're on the subject of falls, here's Biohazard hitting the dirt from CB09 in London:
http://www.flickr.com/photos/w3bbo/3855311576/in/set-72157622131665912/