I see many recommendations to make SWAP space equal to your physical RAM or TWICE your physical RAM, however, I don't think those rules hold when you start getting above 1GB or so of RAM. The only reason to have SWAP is when you run out of physical RAM, something that is highly unlikely with 16GB, depending on your specific application.
Take a look at the swap space mini how-to here:
http://www.xenotime.net/linux/doc/swap-mini-howto.txt
For my opinion, if you have a system that USES 16GB of physical memory, and NEEDS 16GB of swap, or almost any swap for that matter... you need to get more memory. Obviously this is for a commercial application, and whatever it is serving would be better served without having to rely on that much swap.
-K