It's a good feature but it is often done so horribly it becomes not liked. Rule number one: If you use infinite scrolling instead of pages, don't remove pages. Especially on pages where content is somehow ordered (shops, lists, ..).
I agree it should be done well, but I don't agree you always need pages. For instance, when I use google images, I'm usually just looking for a few specific images in a sea of pictures and I don't care too much about keeping my place in that list. I care a lot more about being able to quickly scan through a very large grid of images, though, which infinite scrolling allows me to do.
The one caveat here is, if you're going to use infinite scrolling. Don't have links on the bottom of the page!
Sites like Facebook do this, and I have no idea why.
Want to "Create a page". Well there's a link at the bottom. But if you scroll to the bottom of the page, it's going to load more content and push the link down.
I just tried it, and the page reloaded 15 times before I gave up... never did get to the link.
On the right sidebar, under "Facebook (c) 2012" should be duplicates of all of the links at the bottom of the page. For the "Create a page" link, you have to click "More".
This is clearly unintuitive, but at least it exists.
Its probably there just in case scroll detection breaks. Some browsers - specifically BlackBerry browser (v4.6 to 5.0) - support AJAX lazy loading but don't support the scroll event.
