E-cigarettes are different enough from cigarettes that it's hard for regulators to figure out how to monitor their safety and use. There's nicotine, but no tobacco. There's heating, but not combustion. Theoretically, they should be safer to use than cigarettes, but nobody really knows for sure. This piece at InsideScience is an interesting look at how we manage new technologies that don't quite fit into any previously defined regulatory boxes ... and why we'd want to regulate them, to begin with.