Client variables storage in production environment?

His statement is completely wrong.  The docs talk about this here: http://help.adobe.com/en_US/ColdFusion/9.0/Developing/WSc3ff6d0ea77859461172e0811cbec0c35c-7fd5.html

Specifically, read this paragraph from that reference:

Choosing a client variable storage method

By default, ColdFusion stores client variables in the Registry. In most cases, however, it is more appropriate to store the information as client cookies or in a SQL database.

The ColdFusion Administrator Client Variables page controls the default client variable location. You can override the default location by specifying a This.clientStorage value in Application.cfc or by setting the clientStorage attribute in thecfapplication tag.

You can specify the following values for the client storage method:

• Registry (default). Client variables are stored under the key HKEY_LOCAL_MACHINE\ SOFTWARE\Macromedia\ColdFusion\CurrentVersion\Clients.
• Name of a data source configured in ColdFusion Administrator
• Cookie

Generally, it is most efficient to store client variables in a database. Although the Registry option is the default, the Registry has significant limitations for client data storage. The Registry cannot be used in clustered systems and its use for client variables on UNIX is not supported in ColdFusion.