There might be some accusations towards Bitgo posted above links ^ .but still companies do make use of it which signifies it is still trustable enough and I don't really see similar thing on the net which do have the same service that they do gave.
Its better to store your coins in paper wallet and use them by importing it in supporting multicoin wallet which gives you private key....
Agree, I would choose up to store coins in a paper wallet and I'm not really much confident into other 3rd parties.