Well, it all depends on what you're using it for. On my desktop (a 12Gb Nehalem), I'm using twice RAM simply because I'm suspending to swap when not in use, and I'd rather like to find I can suspend even if I happen to have launched a monster 20Gb compilation, thank you very much. On the server holding my home directory, though, I don't bother: the machine runs good few VMs, so it has 24Gb RAM, and the max RAM on that motherboard is 128Gb. I'm not configuring 256Gb swap, thanks! I configured 24Gb swap and I think that was probably too much: I've never seen more than 6Gb in use.
The rule for swap is really 'configure as much as you need'. Swap partitions aren't much faster than swapfiles these days, so adding swap as needed isn't penalized anymore.