About four years ago, a small digital print shop based in the UK began offering customized photo books. They ran a Facebook promotion, and, expecting a modest bump in volume, the shop was shocked when the promotion went viral and orders poured in by the bucketload. The small staff and limited equipment had to work around the clock and on weekends to keep up with the demand — after all, criticism of the shop’s service could just as easily go viral. Although it’s been said, “that’s a good problem to have,” it wasn’t really. The company did manage to fill all of its orders in a timely manner, and …