Agreed, anti-virus runs with elevated privileges, and downloads rules/code from a central source. So any compromise in the anti-virus client or the server it d

Agreed, anti-virus runs with elevated privileges, and downloads rules/code from a central source. So any compromise in the anti-virus client or the server it downloads from can cause serious security issues. There's been numerous reports of bugs, exploits, and really stupid behavior like man in the middle attacking all certs, and "forgetting" to check if the certs were valid. Similarly false positives can cripple a machine. Some anti-virus companies even put malicious entries into the anti-virus databases to try to trick the competition from banning clean files. So there is a security cost, CPU cost, memory cost, I/O cost, and reliability costs. It's far from clear that anti-virus makes sense on any platform. Sure the major vendors are pushing FUD to keep the income stream going. Obviously compromising an anti-virus company would be huge win for an attacker, so it shouldn't be a surprise they are common targets, in particular NSA and GCHQ have both targeted anti-virus companies. In my experience users of OSX and Windows have MUCH less functionality out of the box and need MUCH more of the dreaded google for software and download from a random site, thus the higher need for anti-virus.