i personally dont think the risks are exceptionally high as long as you are keeping just females together. i wouldnt be keen on keeping larger numbers together. i have some pairs of females together who are happy to curl up together. some say this is just becausethey are forced to share the same space but if they were really hostile it would show in their reaction to each other, one would go cold most probably in order to stay away, not 'share', and they would be stressed too affecting their feeding. It is of course possible that some individuals may react badly to this situation, because they all have personalities, and if this is the case, be prepared to separate that one. none of mine are noticeably stressed however, in fact they look very content. this issue is very taboo on forums however in real life cohabbing corn snakes is very common and often they get on ok. cannabalism is more common i think in hatchlings that are all left together, however there may be other factors involved...i mean, such as large numbers in a very tight space so they cant isolate themselves. I have to say some of my hatchlings are hard enough to get to eat a pinky, let alone each other, and i wonder if the snakes in question are under stress...? it is a rare event. I have also heard it happening when larger, keen-feeding snakes are kept in with smaller ones, again perhaps in a small space, maybe under stress, under fed....i mean you don't know when you hear these stories do you?
Do not keep males in there. i have a yearling who has already shown he recognises a female's scent and tried mating! Can you imagine a snake as young as that pregnant? It's dangerous for them, and it would happen if you left them all together, and if the eggs were laid you'd then have to incubate and hatch and care for them- year after year prpbably and females lose weight when they produce eggs, especially since they usually starve while gravid. It's a strain on them. contact with males also encourages egg production even if they dont mate so your snake could produce 'slugs'- infertile eggs which are much more likely to get stuck and cause a life threatening situation. they can do this anyway, but you dont want to increase the chances. Not to mention the fact that a male with persistently try and mate, getting very frenzied, over a looooooooooong period of time, even if he has already fertilised the female...driving her loopy. and ptentially even injuring her. they cant get away when theyre locked in together.
a group of males is something i also avoid, since in general, i am not sure if it is true- my 3 males seem slightly less tolerant and friendly than the girls and i have read they can fight with each other if you put them in together. probably some could get on. but i just avoid it anyway.