After reading this thread so far, I guess my group is remarkable in that they rarely fail. In fact, I can only recall two 'failures' in multiple campaigns in 30+ years.
It usually doesn't go smoothly but at the end of the day, they have met the objectives and usually without drawing the ire of the authorities, their employer, and every power group and organization within 100 miles.
I attribute it to my players being very goal oriented and well, outright paranoid.
They are so paranoid that they have expectations of betrayal from almost everyone, including their employer, so they always take pains to find out as much as possible about their associates as they can.
This actually happened in one campaign start that happened after another campaign ended with various 'allies' attempting to screw the party over.
Merchant: "I want to hire your group to deal with a problem that I am having..."
Character A: "Provide three references who can vouch for your character and your abililty to pay. If you check out, we will consider your request. Don't contact us, we will get in touch with you as to the suitablity of your offer. Then we will tell you our terms..."
