I think the simplest and most pressing reason not to keep snakes together is that they may decide one day to devour their cage-mate.
Rare in ball pythons? Certainly not common. Unheard of? Far from it. "Cannibalism is a small but present risk" should be enough to dissuade most folks who care about their pet snakes.
Apart from that, even if both snakes are healthy, have been properly quarantined for a year, and are both female, there's still the possibility that they quite simply will not like it. Ball pythons that are unhappy tend to express this by fasting.
If you don't know your snakes' genders, place two males together may result in a WWF slam match, which is stressful, strenuous, and may result in bruises. If male and female, they will most likely breed at some point, and that's something you're better off planning.
The snakes will spend their entire lives in your care...why not ensure their lives are as stress-free as possible?
Bull friggin crap donna. You know this isn't true yet you keep harping on it. Buy a new record, you obviously have nothing to contribute that isn't tired and wrong.
I may not be very smart, but what if I am?
Stinky says, "Women should be obscene but not heard." Stinky is one smart man. www.humanewatch.org