I’ve purchased several games from eBay in the past by buying Steam codes that I can redeem on my Steam account. However, I’ve noticed lately that a lot of eBay auctions are not for codes; instead, they ask for the password to your Steam account so they can log in and add the game to it, such as this auction here:
No Man’s Sky Auction
Are these auctions scams? If so, what do they hope to get out of it? You could always change your password within minutes of getting the game. If not, why would a legit purchase need to log into your account?
At their most legit, they are sellers from regions where the game is cheaper (China, usually). Steam no longer allows cross-region trading so they can’t give the game as a gift but they could use your account to purchase it “in region”. Obviously this violates the Steam terms of service in numerous ways. Steam can also require a region check when launching a game – it’s not enough to buy/activate it in a region but it can only be launched in that region as well. No idea if NMS has that restriction.
Less legitimately would be access to your Steam inventory (you may not have stuff of value but many people do), Steam wallet (buy & gift games) and, of course, overall access to your account. This is probably less of an issue now with multilayer authorization to do anything of consequence but I still wouldn’t want to risk it.
It’s not like Steam games are all that expensive anyway…may as well just pay full price.