Although I think it severely impairs the value proposition of using InfoPath, I get asked a lot how a company can deploy InfoPath to every desktop and yet control who has the ability to build and post new forms. It turns out that it's pretty easy to do via the Adminstrative Templates that ship in the Office Resource Kit, and those settings can be enforced via Group Policy Objects (GPO's) via Active Directory. To see how this can be done, you need to first download the ork.exe file from http://www.microsoft.com/office/orkarchive/2003ddl.htm and run it. This will install the ORK toolset to your machine and put the administrative templates for all the office apps in the right directory automatically. Next you would run mmc.exe from the Start|Run line, and then add a snap-in for Group Policy. From there you would expand the tree in the Local Computer Policy, right click on Administrative Templates under the User Configuration section, and click on Add/Remove Templates. In the list it presents to you, there will be an entry for INF11.adm, that's the one you want. Once you pick it, you'll traverse the tree as follows:
Microsoft Office InfoPath 2003
Unde miscellaneous you'll see an option for Disable InfoPath Designer Mode. Set that enabled and check the box to disable the setting, and you'll find that the Design button in disabled in the interface in InfoPath. Deploy that setting to a population that you want to prevent this kind of capability to and you're done!