One of the only free documents I could find on toxins in coffee:
Ochratoxin A in Roasted Coffee from French Supermarkets and Transfer in Coffee Beverages: Comparison of Analysis Methods:
"Thus, the intake of a high coffee consumer who drinks 640 mL of coffee (1 bowl of 300 mL at breakfast; 1 cup of 85 mL at 10 o’clock; 1 cup after lunch; 1 cup in the afternoon; 1 cup after dinner) will reach 530 ng. For a human weighing 60 kg, this intake via coffee corresponds to half of the tolerable daily intake of OTA established by JECFA (joint expert committee of Food and Additives) . This intake of 530 ng is six times higher than the virtual safety dose (VSD) (1.5 ng/kg bw/day) established on the kidney tumors ! If we make the same calculation using the average OTA content (1.5 µg/kg) found in the coffee, the amount of OTA in a bowl is 31 ng; and in a cup of expresso 8.8 ng. Thus a heavy consumer will have a daily intake of 66.2 ng/day equivalent to 1.1 ng/kg bw/day, which is close to the VSD. It should be kept in mind that excessive coffee consumption (more than three cups a day) was implicated in upper tract transitional cell carcinoma and bladder cancer [45,46]. The risk is higher for heavy coffee drinkers carrying the genotype GSTP1 105–104 val.  and can be explained by the fact that glutathione conjugation is involved in the biotransformation of OTA into genotoxic and carcinogenic products [48,49,50] leading to DNA adducts [51,52]. As the percentage of OTA passing through the beverage depends on the origin and the roasting process of coffee, the intake evaluation should be done on the amount of OTA found in the beverage. A simple method to evaluate the amount of OTA in coffee could be to extract OTA with hot water. This extract could then be directly used on the IAC column. "
The  and  references in the above study led to these documents:
Alcohol, coffee, and bladder cancer risk: ... [Eur J Cancer Prev. 2009] - PubMed - NCBI - http://1.usa.gov/13nx2Of
Coffee consumption and bladder cancer ... [Cancer Causes Control. 2000] - PubMed - NCBI - http://1.usa.gov/13nxDzh
Basically, you are safe if you drink under 10 cups a day.
Now all this said, bulletproof style coffee is great in my opinion.
The toxin in coffee thing is a real deal. These people (in Europe) are testing for some types and have set "content" limits already. So if Dave is doing his own testing, good on him. Everybody else is unconcerned in America I guess?