P.S. Im probably to late to reap the bonuses, but hacks always happen and I want to be ready.
your concern is valid and I think the only solution you have is contacting the site that is asking for your ID and ask them how are they storing these information and how safe it is. and trusting that they are telling the truth.
I don't think they store it live and accessible for hackers, and hackers so far have hacked the "wallets" of these exchanges not anything else (at least not that we know of)
here's a simple tip. make sure that site your going to submit your ID is a trusted site and legit. you can see that in their
credentials. And of course it its about loaning. dont ever attempt to give that. because they use your identity in other transaction