After running with Activity Monitor open on my desktop and actually managing to pay attention to it, I've determined that the Safari Networking/fan ramp-up results from my visiting the NY Times website and that it can be reliably reproduced.
As I mentioned earlier, the process must be force-quit, and that results in short term fallout such as necessitating the reloading of Safari pages because of freezes, but I've been unable to document the fallout.
I hope the problem will be resolved in the next Safari release, but until it's corrected, I guess I'll just use Firefox to visit nytimes.com and see if there's any way to pass feedback to the Times. (NY Times contacted.)
