You can backup  the entire SPS Portal but restoring a single  Portal Area is not possible at present.

Perhaps with a third-party tool: http://www.commvault.com/products.asp?pid=1

OR

spsbackup.exe, but SPSBackup.exe wont restore  a Single Portal Area will it?? but will a site?

I've been unable to use spsbackup.exe to backup  just an area.

i know you can backup  using spsbackup.exe using the command line