The article implies it's common for recipients to return a lot of the tokens in cases like this. Anyone have any clue why? I would thinks there is 0 incentive to return free crypto.
Just a wild guess: To maintain faith in the system? I don't know anything about Compound aside from what I've read today but I would imagine whatever you've got invested could quickly go to zero if the crypto-investing public decides the protocol is too risky. (Assuming, of course, there exists an upper-limit to their risk tolerance.)
Returning the money elevates the hacker to "hero" status within the crypto community. By keeping the funds they risk getting doxxed and having serious legal action taken against them. Additionally, if the funds are a sizeable portion the entire project might fail rendering their token useless.