Not speaking for James here, but most of what we do is give everyone options
If folks post images that are way too big and/or skew the look of a busy thread, one of us admins will typically scale it down - no problem there. However if you're going to be posting a picture heavy thread, the thumbnails do help help the flow and aesthetics quite a bit
How is that for being politically correct
Personally, I'll be using thumbnails for trip reports which tend to be pic heavy. Calendar thread... Large and 'n charge