most just don't know. And i doubt carbonite is actually knocking anyone offline or anything by itself, but carbonite, among other spammy reasons, are the entire purpose of the 4.1 change. If you run spamalizer (to check just how much addon traffic you send or recieve). you will see there is no addon in existance that sends more traffic than carbonite. Blizz does not like this at all but at same time understands the nessesity of it for addon functinality, thus the awesomeness of 4.1 iltering it for the end users who aren't using x mod. But you would be doing people a favor, if only a small one, to disable it in raids before 4.1. I doubt it's the difference of that 2000ms person you have sitting being able to come in or not. And just one mod, from one user also really is nothing, it's more of a grand sceme of things, 200 mods from x user, another 50 from y user etc, all sending you crap in combat, is what does it. The big picture. It'd take everyone taking action to actually make any kind of diff ,which they wont, which is entirely why blizzard is in 4.1
However I do know that addon memory can have a huge impact on game performance. being a 32 bit app it has a 2gig memory limit. there are hacks to enable a flag to make it 4 but they are not exactly best thing to do (or blizz would be already). ever crashed in a raid from a 132 error? most of those are actually memory crashes, application ran out of memory, often caused by someone with too many mods and high graphics settings. lower grahpics settings substancially reduce heap size then lua memory from mods would be almost irrelevent to a power house machine. But chances are, if your machine is awesome, you are running ultra, and probalby 200M of lua memory too. don't be surprised if you crash on fights with spectacular detail like algalon or something, or a fight with a TON going on like heroic omnotron. Since i love game looking awesome, i def run ultra in raids, but my lua memory is less than 10 MB cause i disable all non raid mods before raid, make sure the client has more breathing room for texture caching and what not
anyway i've strayed from topic but i thought i was vague before on why i feel it's a bad idea to raid with carbonite (since by itself can easilly use 20-50MB).