Is it safe to generate a public/private key pair on the server, add the public key to the authorized_keys list, and then copy the private key to each client, as described here (http://www.rebol.com/docs/ssh-auto-login.html) Assuming you maintain permanent control over each client? (i.e. same user, many computers).
Typical procedure is to generate the public/private key pair on the client, and then add the client's public key to the authorized_keys list on the server as described here (http://www.linuxproblem.org/art_9.html). With this method, if you have several client computers, each much must be concatenated to the authorized_keys list and maintained over time.