> do you believe in implicit agreement to contracts? This might take the form of, e.g. an expectation of refund if this DVD ends up being blank, or the belief that the DVD won't contain a virus or cut you when you grab the edge.
In a word, no. I expect the DVD to work and not have a virus because consumer products are usually subject to an implied warranty of merchantability (which is very much not an ethical agreement but a legal obligation imposed by courts). The idea of a corporation replacing a faulty product because it's the right thing to do sounds like something from a children's book with talking badgers who wear waistcoats and serve tea. The real-world DVD manufacturer would dump toxic waste in my back yard if they thought the savings would exceed the fine.
> they still exist as a set of expectations and assumptions that come with social interactions (including product sales).
Purchasing a product from a corporation is not a social interaction. Not sure what else to say beyond referring you to the definition of "social."
> In other words, are there implicit rules that govern any given exchange beyond those that are explicitly stated before the exchange occurs? Really, rules that govern social interaction generally. Do those rules exist?
There are implict rules for all sorts of situations, sure. People tend to disagree on what they are, which is why we have so many explicit rules, e.g. copyright law and the CFAA and so forth. But sure, implicit rules can exist. "Don't fart in a crowded elevator" might be one. Another might be, "If you have a point to make, explain it clearly as opposed to dragging it out with leading rhetorical questions." What implicit rule is it that you think applies to purchasing stuff?