But let's say you visit an open house, fall in love, and in your excitement, forget to write your agent's name on the guest sheet.

WSJ: Open House Etiquette

This can cause 'fakers' to pretend and write posts in your name.

BBC: A teen guide to staying safe online

Give the listing agent your agent's card, or write his name next to yours when you sign in.

WSJ: Open House Etiquette

Oh, by the way, the letter added, you can tell Amex not to share your credit history if you write a letter to one office and phone (toll free) another with instructions not to sell your name to telemarketers.

CNN: How to fight privacy looters