>>>Overreliance on protective gear, and then less care when moving about. I've once heard about soccer practice (let's see... summer '07) where the number of injuries was about double or worse for kids who grew up wearing sneakers. Those who spent their childhood barefoot got better reflexes and instinctively avoided most of the injuries.
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>>When I played baseball, we wore helmets at bat. I don't know a single player who ever stuck his head in front of a pitch just because he felt protected.
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>What's the average speed of that ball? And then, what's the average speed of a bicycle? Besides, on a bicycle, you usually have some chance to react and diminish the impact. So... not really comparable.
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>Now you got me to think... tennis service can go above 130 km/h, right? Though they usually have the time to react, given that that first ball goes off the further edge of the court (*). I've heard some critiques, though, that some of the stars out there win by simply delivering a horribly strong service, and practically managing to scare the opponent in some near-miss situations. I wonder what would that sport look like if they were allowed to wear helmets.

Against a tennis ball? Jeez!

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>>>I've learned to trust my bicycle reflexes - if I suddenly lower my head, that's probably because there's a thin branch hanging low from the next tree, and my brain isn't fast enough to tell me what it is. But it's fast enough to make me react.
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>>If you're lucky... but that first time you aren't fast enough, you may find yourself wishing you'd had a helmet (assuming you can still wish).
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>I am lucky. Whatever I was doing wrong in traffic or elsewhere always first happened mildly - without any serious repercussions, but enough to give me a pause and make me rethink what I'm doing. That's probably the reason why I never broke anything, while having ridden the bicycle in winter, on ice - didn't ever fall. Had the bike fall under me once, but I landed on my feet, and once I made a 180^o turn by hitting the brakes on the iced slope, so I could see the local bus crawling behind me ;). But that's all. I did fall, wear bandages, get scars on my knee... but that was all before age of ten.

Like I said, you've been lucky. Had your head hit the concrete, we might not be having this conversation at all.

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>When I realize my reflexes are too slow, time to stop driving in traffic.
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>(*) - ok, this Anglosaxon legal system was confusing. There's the court of law, court of whatever unlawful, juvenile court, family court, food court, tennis court, ... and the ball is in your court. What's the verdict on tennis then?