Species that have a reputation for being somewhat communal still need to be housed in a large enough space. You can't cram 4 pygmy chams in a tiny aquarium. You could put the same 4 in a very large densely planted terrarium that allows each animal to retreat from the others, get enough food, drink and rest in peace. Some people have kept Meller's chameleons in loose groups but once again the SPACE and how it is designed are critical. Even if they get along some of the time if females are gravid the males may keep pestering them to the point they end up stressed out, sick, dehydrated, malnourished, or even injured. Captive chams don't have nearly the same choice in where they spend their time, how often they must interact with another cham, how well they can retreat from them. Wild ones might live in adjacent trees or shrubs. Even if they are somewhat close together all the chams "know" they can space themselves even farther apart if they wish. Captives can't, and that makes all the difference.
Territorial species like veileds and panthers (honestly the most likely species the typical buyer is ever going to see) cannot be housed in the same limited space. If you had a room with lots of separated trees and visual cover, multiple basking spots, feeding stations, drinking stations you might get away with it. You would have to be watching their behavior very closely on a daily basis and change things up if any of the chams start to decline. I've housed 3 adult melleri in a bedroom free range. They all tolerated it. Most cham buyers are not giving up entire rooms for 2 lizards. For the sake of your chams...don't try. The typical 24x36x48 cham cage? Forget it entirely.