We did GREAT with these through the Christmas season.  However, in January, the original manufacturer came out with this public statement:

In our advertising we stated that Power Balance wristbands improved your strength, balance and flexibility.We admit that there is no credible scientific evidence that supports our claims and therefore we engaged in misleading conduct in breach of s52 of the Trade Practices Act 1974. If you feel you have been misled by our promotions, we wish to unreservedly apologise and offer a full refund.

I spent weeks in fear that everyone would come back to my shop for a refund!  Fotunately that didn't happen.  I haven't had anyone ask me if we sell them in several months.  I think the trend peaked and died.