"What designer originally came up with the idea that light grey, 8 point text in a thin font on bright white background was the height of sophistication? And how did this idea spread???"
I think apple is to blame by way of the iphone and ipad. Those devices have a weird gamma curve and if you visually optimize black on them they turn out to be grey on other devices.
And since web design focusses on mobile devices these days and the hippest of the hip 'designers' all have apple mobile devices you get terrible readibility and usability on everything not mobile and not apple.
I even have a custom CSS on slashdot so not to make the font dissolve into the background at the edge of my field of view..
Whatever the 'designers' think they're doing, it's wrong.