Satoshi’s reply was blunt about how thin the network had become:
There may just not be anybody else running it right now.
He asked whether Bohm’s IP address had changed, and encouraged Bohm to keep his server online so that new users would have at least one node to connect to when they started the software.
Roughly six months after launch, Bitcoin’s continued operation depended on a handful of early adopters — Bohm, Dustin Trammell, and Hal Finney — keeping their nodes online so that a newcomer starting the software would find someone to connect to.