This research proposes that legitimacy percepts underlie not only community laws but also politeness. If legitimacy is fairness, then politeness is being more than fair. If unfair acts destroy the fabric of society, then polite ones create it. Specifying legitimacy boundaries for computer based social interaction is proposed to be the baseline for designing systems that support politeness. Other conditions are that the parties can communicate, that action choices are clear, and that rights can be transferred. Computer system design could not only support online politeness between people, but also allow polite computing, where software respects user information ownership.