Originally Posted by upallnight

That's the keyword if done correctly. On cars that I track or drive over 100mph I wouldn't trust a plug. The centrifugal force and the deformation of a tire under those conditions may cause a plug to pop and with a rapid lost of air pressure a blowout is a good possibility.

Most, reputable tire shops will either patch it from the inside or sell you a new tire. The liability that a shop takes on is just not worth the trouble of using a plug. Plugs kits are just sold to diyers looking for a cheap way to fix their flat, since they don't have the equipment to demount and remount a tire.