Why It Works
Product planners often fall into the trap of thinking that customers have clearly defined product priorities. Some do. Most don't. When presented with a set of options, many customers will simply say "I want them all" and put the responsibility for prioritizing their requests on your shoulders. Alternatively, product managers often gather feature priorities by working with customers one-on-one and, in the process, and perhaps without even realizing it, again take responsibility for prioritizing features. By engaging customers as a group and giving them a limited amount of resources, you give them the opportunity to prioritize their desires as a group. But that's not where the magic lies. The magic lies in structuring the conversations so that your customers are negotiating with each other for specific features. It is this negotiation that enhances your understanding of what your customers really want.
Time Frame of Action