Good point OverPhil
I would just extend it to employment, services wanted/offered, information...really any advertisement or solicitation of any kind.
This brings up a second question: Who thinks up these cover stories? If a used Maytag washer/dryer for sale is my cover story, I have to assume that people interested in buying the fictitious item will call. Therefore, I have to have (as part of my cover) a full set of particulars at hand to answer those questions, even if only to throw people off. My failure to do so would simply arouse the suspicion of those from whom I'm trying to hide my real purpose and who are likely trying to sniff me out. To me it's a no-brainer, but then I don't think like most people.