Show rubber banding before mouse is pressed -  When adding points, "rubber band" lines are drawn from the previous point to the point being added. Normally these lines are only drawn when the mouse is held down. 

To turn on/off Rubber Banding, do the following:

• Click on the Settings Tab / User Preferences / Look Tab
• Check or Uncheck the "Show rubber banding before mouse is pressed" box to turn on or turn off rubber banding.