there are exchanges like bitalo.com out there that do not take control over the coins at all but have user-side generated keys that are stored only in encrypted form on the servers, combined with full multi-signature wallets and backup transaction so that you can get the coins back, even when the site loses all data or goes completely offline.
People just need to use it :-)
Good initiative, thanks for showing us that this can work, and illustrating how irresponsible and borderline criminal established exchanges are for not adopting such practices.
Think about what Bitstamp have been working on instead: A fancy chart UI for trading and an Android app. Meanwhile, they can't even ensure or prove that cold wallet coins aren't lost.