I always thought that OTB is caused by deceleration if the rider stops too abruptly. But I've found an article that says:
Jobst Brandt has a quite plausible theory that the typical "over-the-bars" crash is caused, not so much by braking too hard, but by braking hard without using the rider's arms to brace against the deceleration...
And also I've found an answer, that supports this argument.
On the other hand, there are also people who say otherwise.
I'd like to read opinions, supported by actual practice or science, on that topic.
P.S. Personally, I only use the front brake while standing on the pedals and never when I'm sitting on the saddle, so I'm more able to control my balance, shifting my weight to the back more or less and bracing against the deceleration with my arms.