As long as it goes up, and doesn't become a frag anvil.
Don't know that I would be leaning over it when placing on top of the other, get a spark from that metal to metal/powder contact and could be "flying anvil owner" thread!
I have seen this done live once, and it is impressive.
There is an old tradition that when a blacksmith opens a new shop he launches an anvil into the air.
Notice the tool he used to scrape the powder flat is a carpenter's level. It is very important to get the bottom anvil as level as possible so as to get a short horizontal range on the thrown anvil.