David,
I agree, this is an issue that should be looked into. This (among several other) problems seems to affect enough customers so that it should be eliminated or worked around at the code level. But, I'm just a customer, what do I know
The email bombardment stopped when I eliminated the "--spider" switch in the cron task and added the quiet mode switch "-q"
Try it with a test item that expires in three days. Set yourself up another account on your forum so that you can start a 3 day ad, and you can place a high bid on it.
What I did was create an auction ad, and a buy it now ad. I did this with enough dummy ads so I could see the output as a buyer and a seller. Just post "TEST AD" so your members don't accidently participate. I wanted to make sure I never had it happen again to any of my members so I really tested EVERY possible ad configuration. Unfortunately, unless you have a time machine, you will have to wait three days to see if your test is successful, but I have a feeling the cron command line re-configuration will work.
Good Luck.