Some of the other things that can cause it: uneven tiller, bow too narrow/short for weight, pulling the bow past its intended weight while tillering, pulling the bow too far during tillering with uneven tiller, and mainly,the laws of physics (wood will naturally take some set, if you start with a straight stave, you're going to end up with some follow unless you reflex it to compensate.) Don't worry too much about it unless it's excessive, some follow is normal and doesn't hurt a thing. Notice in the TBB that Baker describes bows with 1 1/2" of string follow as well-designed and efficient. If you get several inches of follow, it will hurt performance a good bit, but doesn't mean that the bow isn't a shooter. I believe Rod Parsons used to win a bunch of matches or tournaments in England with a bow with about 3" of string follow. Most of the bows you see on here that have the tips even with or ahead of the handle were forced into reflex before tillering. This can increase arrow speed, but can also make the bow less stable and make it a bitch to tiller if it has a bunch of reflex.