In aram, most often the mia ping spam is used on the enemy. For example, my most recent aram the enemy Sejuani flashed in place and then dashed towards her turret. Everyone on my team who saw it, which was all of us, pinged mia a few times since it was random and done for no reason.
It was kinda like using the mia ping as a sort of "wtf?" question. Since, well, it's a question mark. It works when you're confused with what happened for certain things.
Yeah, it gets used for the wrong way but it's not the only one that does. I once had someone constantly ping me to be careful... when I'd just recalled after barely surviving a fight. No, there wasn't an Ezreal, Jinx, Ashe, Draven or Karthus on the enemy team. They just decided for whatever reason to spam ping me to be careful right after recalling.
The best way would be to limit it. The most I've seen them used at once when used correctly, was 4. Someone had caught the enemy jungler pop up on the mini map, and had pinged the 4 possible places for him to have gone. His blue, our red, dragon or bot lane as he was seen closest to bot lane. So I'd say to limit it at 4.