The so-called security deposit is not charged to guests- it is only there as a threat that it COULD be charged. And the onus is on the host to "prove" that the guest did damage (which has to be done within a very constricted window of time), and many times airbnb will consider damage to be "normal wear and tear". Also it cannot be claimed on for guests not following your house rules, i.e. leaving all the dishes encrusted with food, leaving lights and other appliances on when they have been specificly asked to turn them off when not in use.
So, in a word, it isn't something you can depend on receiving.