It's not like they're a constant threat or anything.

[ Because the same story over and over again isn't interesting! ]

And I suppose it would be possible to bring one in. I think there's at least one or two instances of the transporter being in disembodied beings. Not a good idea, though. If it isn't already attached to someone, it would just pick something at random.

Well, either that or angrily kill us all. Whichever. Some of them probably have tempers like that.