Yes, in Facebook's case I do think this feature is very stupid for exactly the reason you state. There is a footer underneath the feed with a few important links. I too have advertised on Facebook and have run into this exact problem. I scroll down, and the footer gets pushed down further.
Just as you said, I think the better solution would be to take a lesson from Google Image Search and have a button that says "Show more". This could still be an AJAX thing, where the information is loaded without having to reload the page. But I think it'd be more natural.