To clarify a bit more on things. There are direct messages. But they are protected by KT(Karma Tokens) and Trust. In any profile you can set how much you trust that person. If I trust A and A trusts B, then I somewhat trust B indirectly. You can set how much it costs (in KT) to contact you for people you directly trust, indirectly trust and random strangers. That prevents random people spamming your inbox.