The down side to laying prone is it limits your vision. I always plan on them coming from a certain direction, which works out for me maybe half the time, if I'm lucky. Just my experience, but game in general tends to pop up sometimes where it is least expected. I don't know how many times I've said to myself, "where the heck did that come from"? I've often wondered if they don't have a sense of when you have your eyes on them and when you don't. And your chances improve from directions you can't see.