Since many Instructables require assembly, the probability exists that something someone builds will fall apart. This can cause a safety hazard when the invention is something someone rides or sits/stands on. Be sure to include a warning of the consequences should that invention fall apart while someone is on it.
And let's watch the speed, folks. Some of these "vehicles" can go very fast. Slow it down, and you'll get there. Speed, and you'll just get injured.