When is it a bad thing to NOT be on a mailing list?

When it is your own project - that is probably the one time you actually want to be on a mailing list.  We just completed a project for a client who had us obtain a mailing list for them that was pretty broad based and her name was not on the list that she ordered and she questioned why wasn't it there - it should have been, according to her.  Since her name didn't show up, she wondered whether the list was even good at all - after all, if it was any good, her name would be there.

Well, the bottom line is that the list compilers don't know everything about everyone (contrary to popular belief).  The names on a mailing list come from a variety of places - from directories, telephone and utility hookups, warranty registrations, subscriptions, purchases etc.   Does it mean the list choice was a bad one -- not at all - especially if it meets the criteria and quantity that the project calls for.