Bent Cassette

We were out today and my friend managed to bend his cassette whilst setting up off a gentle hill. Is there a logical explanation for this beyond it being a duff part . The bike its on has probably done under 250 miles since new or is it just that 10 speed cassettes are prone to failure as they are that bit thinner ?

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cassette[/url] by The_Manx_Ambassador[/url], on Flickr

I did similar to a new 9 speed XT cassette a few (5?) years ago. I tried warranty but it was refused. There were a few other people around who had done the same thing. So not a new / 10 speed problem.

Chain alignment thing?