Neither
http://library.linode.com/linode-platform/nodebalancer-reference or
http://library.linode.com/linode-platform/nodebalancer-howto has the documentation that says the nodebalancers add X-Forwarded-For HTTP header or that the nodebalancer IP range is 192.168.255.0/24. This is really handly to know when deploying servers that use the origin address. A reference to
http://wiki.nginx.org/HttpRealIpModule#real_ip_header would also be useful.
I added a comment on one of these pages that included this information but I guess that's still in the moderation (or deleted) queue (its been at least a week).