Symptoms
Unable to display the system value current user's display name on the smartform data label control.
Diagnoses
After checking the advanced properties of the form, if was found that "Anonymous Access" was enabled. When Anonymous Access is enabled, user context information such as name, display name etc. will not be populated on the view/form as there is no user context.
Resolution
To resolve this, disable "Anonymous Access" on the Form.
See the following documentation for more information:-
http://help.k2.com/onlinehelp/k2smartforms/userguide/current/default.htm_Anonymous_Forms.htm?Highlight=anonymous