There are times that you will not use accountability with tags. For incidents such as some motor vehicle accidents, dumpster fires, car fires, or anywhere all personnel are in plain view of the AO, visual accountability is acceptable, but must be properly documented. Any time personnel operate out of your line of sight, the tag system must be used.
In my experience with setting up accountability systems, it seems to me that proper documentation of accountability has gotten overlooked, until it is needed. Hopefully we can take a more pro-active approach to accountability as a whole, and have it when we need it, as opposed to wishing we had it when we needed it.