Q: Safari taking too much memory

There isn't much you can, or should, do about it. Safari caches everything in case you go back to a page or image. The operating system also manages the virtual memory and will take what it needs. If you are experiencing any undesireable side effects, they are likely due more to the antivirus than the memory.

But look at the bright side - you won't be accidentally e-mailing viruses to any Windows users

ACTUALLY  .... Safari has become the memory hog, extraordinaire, these days. EACH tab ***** up valuable memory and doesn't (appear) to release it. I'm no longer using Adobe Flash which, in and of itself, a memory hog ... but I've had the FaceBook Safari tab eat up to 5G! That is NOT megabyte!! Running Chrome or Firefox, and tapping into the SAME websites, using their tab setups, I use 1/4 or less of the memory used by the likes of Safari. If they can't figure it out, I'm dumping Safari and going with another of the browsers. ONLY way I've discovered to minimize that memory captured by Safari is to quit and reopen ... but that is NOT a solution!! I've attached a screenshot of the memory (vs CPU) used on a typical Safari browse: