Not only is sketching on your own a great way to convey ideas - its even more powerful when done collaboratively. Your sketches, user flows, and product prototyping can become amazingly effective and efficient when the entire product design team is working together.

User Experience and Interaction design professionals usually talk about using this technique to build vision/clarity between teams and stakeholders. It also is extremely valuable for improving pattern identification, creativity, and design quality if product managers and designers from across teams use sessions like this to collaborate.