It seems awkward sometimes that Skype can't have two accounts signed in on the one machine simultaneously. If I have a separate account to Deb, but we share one computer most of the time, then we need to choose which one of those two accounts will be signed in, but we might not have matching contact lists, so, for instance, Deb might miss a chance to talk to an old college friend because they think she is not online. It's a pain to switch accounts, and it's not always possible either.
Mokalus of Borg
PS - The only answer I've seen is to use two Windows accounts and external handsets.
PPS - Or not share a computer.