Hi there. My little wireframing tool (Balsamiq Mockups, http://www.balsamiq.com/products/mockups ) uses a sketchy stencil exactly to avoid the perception that the wireframe is a working prototype, and to help stakeholders focus on the app or site's structure instead of gradient colors, icons etc. I'd love to hear your thoughts about it. I've been following your blog since it started, excellent work, thank you!