1. Corporate abuse (just like Valve did recently and thousands others do every day) - you can't do anything about that. No really anything. The most individual can do is strike corporation where they don't expect, that only work once and for one individual. In all other cases it is pointless - there is just way too big weight difference. And no, the class action suite would only make big corp smile. Valve done this and nothing can be done about that.
2. Individual abuse (download hash table, find passwords, do whatever) - you can confront that, but only in equal conditions. Hacker uses his tools, knowledge etc and user uses tools provided by cloud (in man vs. man case clouds tend to try being all good and protect user). So when Amazon made this security hole they took some of user tools, namely account-content link. This was done not by some evil plan to force users to buy second copies, that would be absurd, but because Amazone didn't care enough - "they want delete feature? fine, enable it for everything and everyone".