As long as i know etherdelta is no,problem when we gotta use it in transaction exchange,co'z mostly all of my co bitcoiners and me used it in times of trading exchange there tokens to ethereum or sometimes sell there to exchange it in fiat.the only disavantage of etherdelta that it is purely ethereum,and you must go to other trading sites to convert your altcoins into bitcoins.etherdelta asking your private key as far as i know that it use for deposit only your token balance into there website for next transaction.,but to prevent this you must create another account everytime that you make an transaction exchange in etherdelta for your asset security.