I've had a guitar shipped to me with no case (one that I bought on jemsite, incidentally) and it was fine, but I wouldn't want to make a habit of it. It was a cheap guitar, so I didn't stress over it, but I wouldn't ship an expensive guitar without a hard case.
I would check the policies of the shipping company too. I would guess that they won't insure a guitar that's being shipped without a hard case.
ask to have it shipped with the neck taken off, this would greatly reduce the chance of some sort of break in the neck or at the bolts or anything like that. I've had a couple guitars shipped to me that were just in a gig bag inside of a guitar box stuffed with paper and stuff that turned out fine. But i think that without the neck it would greatly reduce the chance of damage if the shipper doesn't do much else.