This is not the first time university extension has noted a problem. In 2005, Ryan Miller and Dean Malvick with the University of Minnesota made this observation:

"Crop management decisions based on anecdotal evidence are often costly, and decisions with substantial economic risk are best based on results from replicated research trials. Data from replicated foliar fungicide trials conducted at 65 locations across the north central region indicate applications of strobilurins (e.g. Headline and Quadris) had a positive economic return about a third of the time, however, a third of the time they had positive effects on yield but were below an economic return, and a third of the time they were associated with a yield loss."

The yield gain/loss mechanism associated with fungicides is poorly understood. BASF have themselves put forth several theories on the physiological changes that fungicides produce within the plant but even they admit that they do not understand it completely. However, the potential for yield loss (albeit not at the levels seen this year) has been known for some time but you never heard this info from a chem company. There's a reason why...

I was unaware of the peanut problem. Thanks for the update!