The answer so far seems to be to query *.TLD, nab all the records, and then compare them all the results you get back from querying the domain. If there is anything that doesn't match, you are in the clear. (Modulo internal networks and localhost and all those fun tricks of course--but that's a different problem.)
The fact that this is a single IP comparison with Verisign today presumably does not preclude the wonders of MX records, CNAME's, multiple A records and all of that in the future.
Alg 101 1. Seed the isWildCard[] probability array. Generate N random strings. Attach ".NET" or ".COM" to them. Get records for them. Compare records to each other assigning them probability of being a wildcard based on the repetitiveness of the data. 2. Query domain name in question. Compare the result with isWildCard[] probability array. Alex