I find it quite interesting that folks get all bunched up about Norton and MacAfee products ... with all sortsa "crashed my system", "slowed things down", and "missed this or that" complaints. Interesting because both are highly rated (consistently at the very top of the pack performance-wise) by independent testing organizations, and because I myself have quite a bit of positive experience with both. What this leads me to conclude is that both could use better documentation and user-support, and that even that prolly wouldn't matter much, since folks rarely bother with either resource until things at their end are already screwed up bigtime.
Both are resource-intensive, yeah, and I'd sorta like to see that remedied, but I understand where they're comin' from and where they wanna go with it, so I see no reason to anticipate either will evolve a smaller footprint. As machines, processors, memory, and operatin' systems constantly become more capable, that's less and less an issue. Heck, a contemporary mid-line, mid-price mainstream graphics card today has more memory and computing power than was common for an entire expensive topline desktop computer of 5 years ago
There is no perfect software. A huge part of the problem however is that there are no perfect users, and an amazing pecentage of users seem to go out of their way to be imperfect, then blame the software for not preservin' 'em from their own misdeeds, omissions, and in-general-poor-practice.