It's not inherently more stupid than using NFS at all, at least from a security standpoint. Sure they get all the data rather than dribs and drabs, but still...
On your second point - why would you make a backup share writeable? Duh!
Finaly, ok on checksums you have a point but this is just down to limitations in tar and the article does suggest other tools such as dump. Ultimately he wasn't writing an article aimed at being the be-all and end-all of backups.
Still, piping backups through ssh. That's quite neat, I usualy pipe remote backups through compress, but if I'm working in a nonsecure network I'll remember that.