Broken rocker

Any idea why a (stock) rocker arm would break after only 1K miles?
It's a sbc with a 350 hp cam. The engine has not been abused. I'm just concerned that there could be something else wrong.
Thanks.

Here's Pic.

thanks

Thanks Denny, good info. I will inspect the rest of them for similar wear.
I'm probably going to replace them all with aftermarket roller tips. I hear they're much stronger. Thanks again.