This is so true! I finished a very LARGE site project with all the bells and whistles and provided a reasonably discounted invoice to a customer (who, in the beginning evidently knew it was a paid job “I’ll pay you, of course! Time is worth money!”) Yet instantly forgot once the invoice was delivered and, after taking months to pay the invoice, ceased talking with me on a “friendship” level. Now, every time we communicate it’s via email and it’s an order to change something on the site. My husband, who is friends as well as an employee of this person, spoke with him about it and the guy seemed to think he now OWNED me for how much the invoice was! Although the invoice had an option for site maintenance and a described level of changes — FOR AN ADDITIONAL, SUPER CHEAP, MONTHLY FEE! That, of course, he has never, ever paid.