The SOP shown in the link above describes a nail gun trigger action called 'single shot mode'.

In this action, you need to push the nose into the work to let the safety mechanism depress and then pull the trigger to fire the gun. To fire a second nail, you must go through the whole process again.

Some guns have two operating modes - 'single shot' and 'bump fire'. When the bump fire action is selected, you can keep the trigger depressed and simply bump the nose of the gun onto the work each time you want to fire a nail. Bump fire is handy for jobs where you need to fire many nails in quick succession.

What do you think would be the extra safety problems associated with bump fire mode? How would this affect the way you use the gun, or position yourself before you start firing?