I guess it depends on a case-per-case basis. Just going by my experience where he explicity stated that refunding is at Valve's discretion and they are under no legal obligation per their TOS.
Valve will "happily" refund pre-purchases (if actioned before the release date) and unredeemed gifts as they're unused products. The matter of activated games is something else entirely and unless there's widespread outrage or you can point to the letter of the law that states the company is obligated to offer a refund, the request is all but guaranteed to be refused.