It's impossible to tell but it's curious to think about how much earnings we have lost over our affiliate lifetimes due to error.
Things happen and this is not an ideal world so not picking on anyone lol. To me it's the cost of doing business and the benefits outweigh the loss usually.
Some affiliate program issues:
Human Error
Technical Error
Stats Error
Infinate link changes/rebranding
Switch to new Stats Progam
Mismanagement
Fire Sale
Out of business
Close and Take the Money and Run
Improper bonus dedutions
Cookie issues
Thinking about it it's really hard to say. I'm not large but have been doing this a long long time so I would have to be in the six figures of lost commissions over the years.