I don't understand why people building these infinite-scroll pages don't just make the footer float at the bottom of the screen. That addresses this problem and lets you keep infinite scrolling.
Floating footers/headers are VERY ANNOYING for another reason: when you press Space or PgDown to scroll down, browsers scrolls by 1 screen, scrolling past the content that was hidden under the footer. So you then have to scroll up by a few lines to see it.
In other words, to scroll through a page: Space Up Up Up, Space Up Up Up, Space Up Up Up.
IE and Chrome scroll by a little less than a full screen so you get some overlap, as long as you keep your fixed footer very small, like one or half a line of content text, you should still be OK.
