In Vernor Vinge's "True Names" there is a character in the MC's cabal of hackers who does not appear in person in the virtual space, but their presence is felt there via messages that trickle in very slowly on a virtual teletype machine. After some speculation that it might be the vanguard of an alien invasion, it turns out to be a CIA AI that requires much more processing time to think than would allow it to carry on real-time conversation.