I wouldn't give it to them. Gunny used to eat them before I got her but now i just give her some chew sticks every now and then and she's quite happy. I think they are pushing it but I'm not positive.

 

Pet stores dont care really whats good/bad for your pet... they just want to sell you stuff.
In ALOT of treats there is stuff that could be harmful, or even kill your pet.
I dont have ferrets, but I know in rabbit treats there is all sorts of wierd stuff thats horrible for them- geletin, wich is an animal product that buns shouldnt have cuz they are vegetarians, is found in alot of treats. Corn, wich is indegestible to them, is popular in food mixes, treats ect... Yogies are made of yogurt and milk and what not, wich can acually kill a rabbit if it has too much.
Ive bought hermit crab food that has acually killed a few of them too. :C
I make alot of my own treats and food now to make sure it doesnt have anything harmful in it.
And telling the petstore that its harmful to the animals wont make them stop selling it. Ive tried that before... they dont listen. :\