"Dun and Bradstreet" is a proprietary "business number". For consumer protection, it would be nice if every business had a unique government-assigned number and all ads be required to give that number. The government requires every citizen to have a unique number in most societies, so why not businesses also?

''Most (if not almost all) juridictions register their businesses in a process that assigns a number.''
Furthermore, all businesses can be accessed via many different types of numbers.  A few examples:
*Very large companies tend to have their own telephone number "area code" + "exchange" (NPA-NXX)
*In Canada, Large Volume (mail) Receivers (LVRs) haver their own unique postal code.  The USPS has a similar ZIP+4 capability.
*Work is underway to create a GPS (lat, long) reference that will specifiy the location of both corporate head offices and their Retail outlets.
*Classified Advertising heading codes in both newspapers and yellow pages directories are numbers that can be combined with a few other bits to create unique Keys for corporations in most parts of the world.
* ... ''feel free to add more since the current list is nothing more than a few easy examples that ceratinly do not include some of the more interesting instances that have significant commercial value''...

Obviously it is easy to craft a unique 'Key' for any Entity (Tax laws recognize both Individuals and Corporations and such)  and, in fact, many different Classes of Keys can be created.  

I believe the real issue, therefore, becomes; What is the intended use of a Business Identifier Key (since that will determine the nature of any 'atomic' Keys that should be assigned and any Composite Keys that should be created from the Atomic ones). -- HansWobbe.

''Law enforcement, for one. You need to know who to investigate or who to sue. "Bob's Lead Toys, Co." could be anywhere.''

Enforcement suggests employment of Observation and Surveilance while encouraging compliance with laws and regulations via sanctions, fines, and detentions.

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See also: ArePhysicalPostalAddressesArchaic