As I've thought more about guerilla advertising and how it differs from quality customer engagement that turns customers into promoters, it occurs to me that the key difference is self-perpetuation, or the lack thereof.
The goal of both efforts is to get people talking to their friends or colleagues about your business--to create buzz. But guerilla advertising is based on a staged event or gimmick that may not even be related to the business. Yes, it creates buzz, but that buzz will wear off and then all you are left with is the headache of trying to come up with the next gimmick.
Turning your customers into promoters through quality customer engagement is different. It may not get as big of an initial buzz, but it grows naturally and is self-perpetuating. People end up talking not about your gimmick, but about how remarkable your product or service is. They plant seeds in the minds of their friends that produce additional seeds as those friends give your business a try and spread the seeds to their friends and so on and so on and so on.
Self-perpetuating word of mouth--start planting the seeds.