Hah... I wish this was true. You can put quite a bit of force on a cog/lockring while descending hills, I had a hub I could skid on quite easily on descents, but busted it loose while applying backpressure on a steep descent.

Nothing beats the feeling of having your hub go free while riding brakeless (was eager to ride my new winter beater and hadn't put a brake on it yet) on a major urban descent (think San Fran. steep).

Bailing isn't fun. Brakes on all bikes since then.