I don't see any reference to ZFS send/recv, but a colleague had recommended Tarsnap (
http://www.tarsnap.com/index.html
) for online backups. Pricing looks better for rsync.net though - USD0.20 per GB per month, versus USD0.25/GB/month plus USD0.25/GB bandwidth charge.
Being able to use zfs send/recv directly is attractive, but I'm not clear how you'd handle encrypting the data. I reckon you'd have to setup the local ZFS volume with encryption, but I don't know if the remote system could handle the "receive" without access to the key... Maybe I'll sign up and find out. Thanks for the tip!