@deathhero61: he doesnt need to go all out to nuke cities or just wreck the planet with some blast.
If he stops to chat he can find himself in a genjutsu because we dont get an explanation on the rules of ki, but a lot of the characters show telekinetic, telepathic and blowing things up with their minds in dbz including goku. Gohan and krillin have even sparred eachother entirely within their minds (imagine invading the mind of guys who frequently fight others in there). Hell, no one flies in dbz without telekinesis, the rules there work the same way most telekinetics can fly in comics, just much more aggressively. Look at majin vegeta, babidi's mind control had next to no effect. Veget put the supposed "controller" in a box and found a corner for him essentially and kept only the benefits.
The entire ki concept seems to be mastery of the mind, thus there's usually a good few clips of meditation. So we really dont know how far genjutsu can go against these guys, wouldnt be surprised if someone succeeded, wouldnt be surprised if goku broke out.