Hey now, I'm one of those with a current mite problem. I take preventative measures against mites, my newest is in quarantine and has been pre-treated for mites, and I haven't even been to a pet store in a month and a half. My newer snake isn't even the one with mites, it's the one I've had for a while. (I really don't know where they came from...) I just treated my entire rack not even a month ago when I received it, even though there's only one snake in it.
I'm not especially experienced in ball pythons, but I think I'm really anything but careless. I try really hard to do everything right, and stuff happens sometimes that sucks... like mites, for example.
I have noticed that there has been a lot of reports of mites on here, though... It's just that whats so awesome about forums is that you can ask specific questions that fit your exact issue and get an educated answer for it.