Mazda Repair: Front left wheel bearing Mazda 323, front wheel bearings, flood water

Question
Mazda 323 2002/03
I had a front left wheel bearing replaced in October 2007. One week later the humming noise returned. The new bearing was replaced (again) July 2008...no noise so far. The mechanic who did the original replacement wasn't pleased when I asked why a new bearing would fail. He suggested that the bearing could fail by "hitting a kerb" (no bent wheel or damaged to the dress rim noted) or he "may have bruised the bearing putting it in". He quickly offered to refund my $$$.

What could cause the catastrophic failure of 2 left hand front wheel bearings in one year?

Answer
Based on what you tell me my thoughts are the original bearing as an assembly was not replaced.  I suspect it was simply cleaned repacked with grease and refitted.  Bearings are tough parts that don't fail easily.  Hitting a curb, accidents that involve impact to a wheel or flood water driving can lead to bearing failures but even then it takes hundreds maybe even thousands of miles before a problem will manifest itself.  You got a refund without a big fight, he knows what he didn't do.  No brainer advice?, steer clean of that shop.