The blue ring <from what I have read> has an average life span in two years, in captivity they tend to only like a few months to a year because they tend to be collected at 6 months to 18 months old, most are adults when the hobbyist recieves them.
As far as wether it is responsible or not to keep one. That really isn't up to the LFS, it's up to the person looking to keep one. And while I personally, as a store emplyee feel that the LFS should question the persons knowledge of such a dangerous creature before ordering one for them, they should also question the equipment the person will be keeping it in, and the other possible risk that the person has in thier house, such as children.
I don't think that owning this specimen should be considered anymore dangerous then owning a gun, a car, or anything else that has the potintial to kill you.
I hear a lot of people that post things like owning one is irresponisble, and asking for trouble, death wish, etc...
Well this is the same argument that people have used for gun control laws, these are the same arguments made when the goverment decided they would start testing people for thier ability to drive a car.
From what I can find there have been three reported deaths from blue ring, in fact I only found two, but another poster on here mentioned three. but the blue ring has been available for a long time.
So this leads me to believe that either someone is being responsible, or they are not taking the risk.