I've been helping someone setup DNS—more specifically, so he can control the reverse lookups. I use NS records [1] but according to the documentation of BIND [2] and RFC2317, [3] you're supposed to use this horrible CNAME hack. The only thing I can think of for doing that, beyond the Complexity for Complexity's Sake Syndrome, is to avoid confusing a person over having to configure an IN-ADDR.ARPA domain they're not really delagated to serve.
I was told the trick by my friend Kelly [4] who used it for his home network. He sat down and applied some thought as to how DNS works and came up with this method.
I like it better than the “official” way.
[2] http://www.isc.org/products/BIND/docs/bind8.2_master-file.html