-- Tue May 31, 2011 7:02 pm --
Whoops I totally neglected to consider it being virtual, that link's just about swap space in general.
Truth be told, I can't give a definitive answer but depending on the RAM usage you foresee on the v. hosts as well as available disk space, if neither are bottlenecks for you, I'd allocate swap for virtual hosts as you would for any other.
"I'm going to get into your sister. I'm going to get my hands on your daughter."