At this point, over 1/2 voted they would run away from a screaming good deal on a firearm. But what if that was the only indication that it might be stolen?
What if the same seller was selling the same item at a price more in line with the actual value. Would the buyer, without the benefit of the warning of a low asking price, buy the same item without worry? Stated differently, is the selling price that big of a deal?
In FTF transactions I ask for ID and the usual questions to ascertain information about the seller and the item. Sometimes I get a bill of sale and sometimes I don't. It used to be more important to me than it is now.
However, when I go to a yard sale and see a valuable X item marked really low, I don't question it's origination. If I want it I buy it. Some of these items could theoretically have been stolen, or heck even sold by a family member that isn't the true owner.
Bottom line is that I don't think we should fall prey to treating guns with some mystical properties like we have been brainwashed to do. Guns are purely objects. Until recently they didn't have serial numbers and background checks were not needed. You could walk into a hardware store and buy 'em up by the handful with no questions asked. I try to resist the urge to treat them differently when buying and selling, but sometimes I fall back into the mindset of a bill of sale, and sometimes I don't.
I'm also a fan of no-paper trails if possible.