That's right...My salesman in So. FL had never even heard of multiple deposits...or that's what he told me (my hubby always leases his BMWs and they DO take multiple deposits). It's a great way to earn some interest on your money and lower your MF...if they'll do it.If you have the cash up front it may make sense to apply multiple security deposits - which then lowers your money factor - which then lowers your monthly payments.
It amounts to a 3 year loan with about 12-15% return based on the money you're saving on the "interest" (money factor), because you get that full security deposit back at the end of your lease.
Not all dealers will do this however, because they make their money on that interest. Definitely work asking about, however.