I've been doing this. (Score 4)

This has been one of the features I've been trying to hype for our new Web server cluster. I love wildcard A records. There not only useful for non-cookie sessions (I *hate* cookies.) but I have been playing with them to support being able to "log out" an HTTP authenticated connection. (So you'd authenticate with auth1234.foo.com and then the server could invalidate your authentication with that specific host name.)

I have public examples of my use of wildcard A records through purdue.org:

• http://grandprix.purdue.org/
• http://radio.purdue.org/
• http://w9yb.purdue.org/
• http://news.ece.engineering.purdue.org/
• ...