You don't need it on some systems, however Linux will typically kernel panic if it has no swap rather than just killing processes. FreeBSD/NetBSD/Solaris all do

You don't need it on some systems, however Linux will typically kernel panic if it has no swap rather than just killing processes. FreeBSD/NetBSD/Solaris all do this properly, however its still good to have swap because having your processes die when you make a tiny mistake is rather irritating. This is a great example of why you need experienced ops people to reign in the ideas of green engineers.