Mine failed with a tight bolt. The welds were fine, not enough rust to blame that, it is just a weak part and the metal tore out. Some very rough roads at speed. It did last 78,000, but when it failed, it did a number on the fairings.
This is a pretty common problem, though most people report the bolt loose. Then the threads saw though the metal. Guy by the name of Steve Pronto was offering a solid steel block to weld on in place of the stock mount, IIRC he wanted $75 for it. Others have posted pics of welding various metal bits over the stock mount to reinforce it. I have heard that some prefer to use yellow rope.
EDIT: FRH87 posted while I was typing, the third pic is what my '88 looks like. My '01 hasn't broke yet but I'll get some metal welded on there anyway.