Let's see when it might have come in useful:
My worst encounter, when I was injured - I still have the teeth marks on my leg: it was all over so quickly I wouldn't have had time to use it. "I'm sorry, he only attacks tall lady joggers" is my lasting memory from that one.
The large black hound snarling and scratching my leg: it might have been useful there - I don't see how it could have got worse.
The big 'playful' dog with its paws on my shoulder: I'd worry about how close its teeth were to my head, if it turned nasty.
The large white poodle 'playfully' clawing at my heels?: Could have been useful there.
The medium sized dog running full speed at me, barking. (Why I chose to bark I don't know!) It scared me so much I contemplated jumping the sea wall, rather than having to stand and fight it. Fortunately it responded to its owners calls and I wouldn't have needed the dazer.
The whippet that got mud all over me: might have been useful.
The yorkie, snarling extremely aggressively, straining for all its worth at the end of its lead: that would have been an interesting test of it, as I was 'safe'.
The farmer's collie, during a race, which already reduced the woman ahead of me to tears, and was now slowing me down, refusing to head my aggressive shouting: it was a race. Why would I have been carrying a dazer?
The Heinz57 that ran out and tripped me over during a race, giving me a groin strain: again, a race - I wouldn't have been carrying a dazer, and it happened too quickly anyway.
Have I had more than my fair share of dogs?