depends on how frequently you ask that question although it would be courteous of them to drop a quick line.

a couple times over the years, i asked sponsors if there was a problem only to discover that their join page was broken or a similar issue. but i notice that most of the people who start those "are sales down for you this week?" threads seem to start them rather frequently.

sometimes sales are actually down but often it's just the law of averages - every three weeks webmaster a may make 50 sales and the fourth week he may make 25 and feel sales are low. yet if he checked his monthly sales across the last year, he may discover that he's made between 170 and 180 sales every 4 weeks for over 12 months.