It should be restricted to something insignificant, like drones or cannon-fodder redecos - like the Minispies from 1985... The toys themselves only had the rub sign, but were randomly packed in with other TFs toys, so you had to get them out and rub the black square to find out if you had another Autobot toy or Decepticon toy in your collection. It defeats the purpose doing it with established characters, or with the allegiance symbols/bios on the packaging.

But I'm more annoyed that it means there probably aren't any allegiance symbols painted on these RtS toys, which I like seeing on them when displayed.