I'm under the opinion that for low speed work, like a trail bike or tractor its ok, but when up in higher speeds it can ball up in the tyre causing it to lose balance.
There are safer options, I've been thinking of getting one of these kits, they have been getting great reviews and will fit under the seat on most bikes. They are like a key that screws in to the puncture, then you snap the end off, and refill with the CO2 cartridges.
Either that or the bush mechanics here just shove grass in the tyre!
Kenma Australia: Performance Motorcycle Accessories, Cargol Turn & Go, The only way to fix a flat tyre in 30 seconds