Issue:

When browsing to the InfoPath web service method and invoking the WhoAmI web service on a SQLUM (non-AD) environment, no name is returned.

Workaround:

Browse to the web.config file (<install Dir>\WebServices\InfoPathServer) and change the Authentication Mode from the line <authentication mode = "Forms"/> to "Windows".  This will ensure that the WhoAmI web service method will work but might impact the other components in the RuntimeServices webservices.