Ever heard of Ninja Rocks? I was reading on the Honda Twins site and apparently a guy had the porcelin parts of his plugs broken off and stolen. A guy suggested that these were used for "Ninja rocks" and here is what I found:
http://www.mi-reporter.com/news/99324529.html
[ame="http://www.liveleak.com/view?i=a5d_1257946254"]LiveLeak.com - MythBusters - Spark Plug Ceramic Versus Car Window[/ame]
http://www.mi-reporter.com/news/99324529.html
[ame="http://www.liveleak.com/view?i=a5d_1257946254"]LiveLeak.com - MythBusters - Spark Plug Ceramic Versus Car Window[/ame]