Inifiniscroll is great. When used properly of course. Google images is the poster child for this and it works so great because they basically have infinite images. The pattern breaks down when it's forced into places where you have less than infinite content. Much less than infinite content.
I've seen a few examples around the web where content is just continuously loaded even if it's not new content. Take for example the ghost theme repository:
Note the search selections on the scroll bar. After all the themes have been brought in it just starts bringing them in all over again.
Careers.stackoverflow.com sometimes doesn't even try to space them out at all.
This always leaves me feeling like the site is trying to waste my time and fake having more content then they actually do. Getting to the bottom of the page signals that there is no more content. Time to move onto something else.
Infiniscroll is alluring for a bunch of reasons, but please, get the paging right.