If you're running a 32-bit OS, then 4GB is it (Score 1)

If you're running Linux on IA32 then you can only address 4GB. Swap just extends your physical memory, so physical + swap cannot be more than 4GB.

So ... if you have 2GB of RAM, up to 2GB of swap could conceivably be useful. If you have 4GB Of RAM, then there's no point in swap at all.

These considerations go away if you use a 64 bit OS, of course.