I've never used a satellite link before.... haha :D but why use skype with it's big overhead when you just need to exchange some plain text information...?

actually I use skype mostly for text chatting, and it works great :)

I know some small businesses where skype is the primary way of communication, and they even publish it on their contacts webpage instead of phone numbers :-)

Regarding the security -- you just don't have to use public channels for secure information. Your brain is your best firewall :-) so, I don't care much about an closed-source application which works for 99% of my needs (although I do prefer open source software at the server side :-)