Instathread is a service to enable quick ad-hoc "protected" discussion threads.
You create the thread, share the private URL with your friends, and discuss. The discussion is as private as the URL is so keep that in mind.
Sometimes you need to have a quick discussion about something without SPAMing your email or SPAM Twitter or Facebook with a trivial conversation. Need to discuss lunch plans? Instathread it.
I don't know, print it, do a save-as or use some other service.