Do units always prefer the most dangerous route?

[Xiao Xiong]

Well one reason is that it expose it to capture by other civs who would not otherwise attack it.

Yeah.. the only time to do it is when the remaining barb camp is in "your" territory away from other civs and you're already getting around to wiping out the barbs. Earlier and you can't be sure you know where the nearest barb camp is anyway so you can't predict where he's going to go. I find it is pretty often the case though, usually that barb camp is sitting on some prime land and the only reason I didn't settle it earlier is.. the barb camp was there!

 

[qemist]

Mouse over the fog with your settler selected. If you find a red circle there's a hidden barb.

I always eschewed that on the grounds it is a bug.