I went to a lecture the other night and Dave from Safe in Rochester made a great point about why he carries 3 mags with him...
Its not necessarily for additional ammunition but rather in case the magazine in his gun malfunctions. In the event one needs to use ones gun there is not time to take out the mag and see why its not working.
Drop it and hope the next one works better... (if you even have that much time)
BUT - I am now carrying 2 mags because i hadn't thought of it that way ...now if i could just find some pre ban hi-cap glock mags!
Just thought I would share
BTW anyone in rochester - his $10 lecture was worth it IMO especially if you are new to CCW. I am going to take some of his tactical courses...i will advise how those go after i take em'