Interestingly the approach I think works the best (except for the poor input experience on anything that isn't a touch screen) is infinite horizontal scrolling since the footer and header elements remain expectedly stable while not overlapping any information the user wants to view... horizontal scrolling is very poorly supported by input devices and using the scroll wheel to move left/right makes the user think too much.
Oh, but there is a visible load time still. Unless you're browsing on a supercomputer with infinite RAM, after a minute or two of scrolling Facebook you'll realize the performance drops fast with the amount of feed you've loaded, while the load times increase. In my experience, both the page slowdown and load delays are about O(n) with respect to the side of the feed, but I haven't measured it precisely.
In the case of reddit, infinite scrolling is one of the most common reasons I hear used to explain why other users opted out of Reddit's new UI.
the problem is people who cargo-cult Facebook and use infinite scrolling in their business apps which don't have ads