Possible Duplicate:
Why should the size of the swap partition be double of the RAM size?
Does the rule of 1.5 *memory= swap still apply in these days where systems can have32 GB of memory. Besides the fact that it is always bad for a system to start swapping.
Yes, there are reasons.
Most notably for linux desktop PCs, you'll find that you cannot do hibernation without any swap.
Servers with very diverse use might profit from using more memory for file system buffers and sending some unused processes to swap for that (like, for example, mailman processes on a not very frequented mailinglist). Keyword here is swappiness (link goes to askubuntu, but it mostly applies to linux in general).
