OK, I'm sometimes guilty of this. I have replaced my 18,000 Pixels wide pano a few posts below with a shrunk version for web display, 2400 pixels wide. I considered making the display image 1200 pixels wide but that looked so pathetic on my home display that I couldn't bring myself to do it. The 2400 also looks better on screen when it comes up reduced a further 1/4 in the web display.
I'm pretty sure that it is not the forum that is doing extra work when we post a big image. My server has to send it to everyone who links, and then each of us runs an applet on our own computer to perform the reduction to 1200 pixels. But the applet does a pretty decent job, better than I was getting using the tool provided in Apple's Preview. Maybe not as good as if I prepared both large and small versions in CaptureOne, but then I would have both copies clogging things up. Grrr. I recall Jono also complaining about the headaches of shrinking before sharing in his workflow.
scott