This is why we don't put the messages on the blockchain. You also have the issue that the blockchain would store your conversations forever, even if they are encrypted.

So what do we use steem for? Just for the keys. That way you and I can check each other memo keys directly on the blockchain. Then everything else use a good old database.

We are planning to release it live pretty soon I hope. That way people will test and we will have feedback and a lot of bugs most likely.