Trade tariffs between countries, one country imposes tariffs on imported goods, the other country responds by placing similar tariffs on the first country's imports and it escalates creating an all out "trade war," tit-for-tat each country retaliating against the other's economic actions. Do you agree with this type of behavior?

Neighborly disputes or conflicts...for instance, if one neighbor plays loud music late at night, the other neighbor might play their music even louder the next day, escalating into an all out neighbor against neighbor confrontation. Would you retaliate?

Bittorrent file-sharing strategy...in this world of file sharing, a tit-for-tat strategy is often used. Peers share upload bandwidth with other peers who are also uploading to them. A bittorrent client will restrict the connection to a peer that is not sharing and instead offer its upload bandwidth to another, more cooperative peer, creating a tit-for-tat exchange for download and upload bandwidth. What would you do if someone does this to you, would you do the same back?