Nope, no deposit back in my opinion - BUT...only if you have it in writing that the deposit is NON-refundable. Remember, in this line of work, you can't depend on anything or anyone!
I use a 2-week non-refundable deposit, which becomes their first 2-weeks of care (which is also the trial period). This deposit saves the child(rens) spaces, and prevents me from advertising that space. I tell them this at the interview, and it's also in my manual.