I don't even want to think about the hygiene or personal care aspect
Eurgh! I hope they use loads of loo roll to avoid finger poke-through
I also think that if you know you're going to have your talons in a close-up (the Diamonique guest, not Allison), make sure they're freshly done and don't show a chunk of new nail growth under the falsies. It doesn't look attractive and makes the talons-owner look unprofessional (though having fake talons in the first place makes women look that even without the upkeep).
We have a young female GP that has talons. She makes me shudder! When I was in the NHS we weren't allowed painted nails nor could they be longer than finger length.