It would not be comfortable to ride without a seat, and the seat is one of the easiest things to steal on a bike. I don't know why someone would actually want to steal a seat. I mean the sweaty waste orifices of the owner rub up against the seat for hours and hours - I don't know about the rest of you, but a used seat would not be that appealing to me.
Anyway . . . To keep people honest I do employ a seat lock. It certainly don't use the most burly lock, if someone really wants my seat that bad (I am told I do have a nice ass) they are going to get it, but they will have to work a bit for it. It's a simple cable with a combination lock.
I looped it through the arms that connect my rear rack to the frame and then through the rails underneath the seat. To keep it from banging around I connected the cables to the rails with zip ties.
After riding for a bit with the lock like this I did choose to add a bit more style by adding another zip tie to bring the cables together. I simply cannot resist any opportunity to utilize another zip tie.
Total zip tie count to date: 10.