If you'd asked me a week ago, I'd have said that writers' groups don't buy books. Most of the time when I speak to a group of wanna-be writers, they're there to pick my brain, and the enticement of reading my work evades them entirely.
Then I meet a group that surprises me, and I have to run to the car to get more books (always more books in the car--that's a rule.) And I take orders from more people who didn't come prepared to buy the book but want to send a check.
The same thing happens in other places: the library talk goes well but everyone walks serenely by the book sale table. At craft sales, people often walk by laden with those items that make you cringe to think of them garnishing gardens and cluttering kitchens, but they shun books like they reek of H1N1. Other times, people come up after a talk or at a craft sale and buy three books, "One for me and one for each of my daughters." YAY! We love those people.
We just don't know when they're going to show up, or where.