Hi,
I was just browsing through the latest edition of the O'Reilly
DNS/BIND book, and ran across a bit on pointing a CNAME record at
another alias:

"The answer is yes: you can chain together CNAME records. The BIND
implementation supports it, and the RFCs don't expressly forbid it."

The authors go on to recommend against it anyway, but I had always
thought that this was actually illegal.  I don't remember now where I
had gotten that idea... I think the issue had to do with not being
guaranteed that the server would always do the additional processing
to ensure that you got to the canonical name at the end of the chain.

I guess I've been mistaken?  :-)

-C