This was inspired by a comment in this week's Ken and Robin Talk About Stuff.
Suppose that superpowers are somehow psychic, and the higher the concentration of superpowered people, the more powerful they are. So the Hulk is strong when he's all alone in New Mexico, but he's really strong—maybe the strongest one there is!—when he's near three other supers. It doesn't matter if they're good guys or bad guys; Superman is strength 8 when he's fighting Lex Luthor, but he's strength 10 when he faces four Kryptonians. (They, on the other hand, are already at maximum strength when he shows up, so they don't get any stronger.)
So, you know, supers would travel in groups.
I'm not sure how you'd model that mechanically in ICONS or M&M But it'd be easy in MHR.