Linking to page x of result set y so you can send it to a colleague...
Or even say I've scrolled dozens of pages down, then navigate to a link, when I use my browsers back button I'm not back at the top of a list with no way to easily get back to where I was.
1) As a user is scrolling, you can use PushState to update the URL to provide actual linkable pages. It does make re-clicking that link in the future odd though because that page's results are now at the top of the screen so scrolling up doesn't really make sense, but it at least provides the ability to deep link.
2) Sites like Pinterest solve this by opening an item's details page on click in an overlay above the infinite grid. That way when you close it (or click back in your browser) the modal just gets dismissed and you're right where you left off in the infinite scroll.
Sorry, but I strongly believe infinite scrolling creates more problems than it solves - and I'm not entirely sure it solves much of a problem in the first place; the "consume, consume, consume" mentality that it's oriented towards is great for things like news agencies trying to push as many stories as it can to its readers, but this is an archive of content to be browsed in a more... thoughtful manner.
It sure does when it's used inappropriately. But can you imagine Pinterest, say, without it?
Sure it sacrifices findability or reproducibility of a view in exchange for discoverability and presentation of new content but that sacrifice works - and IMO it can work for an archive.
Provided items of content can be found, can be tagged by users (bookmarks anyone?) then if you're targetting the presentation of continuously updated content sources infinite scroll is fine IMO.
Do you have a problem with HN because one can't link to a specific view of a list of stories? Or with Google because SERPs change? Or with your favourite blog because the front-page updates with each new post?
2) There's nothing inherently wrong with "consume, consume, consume". I don't think anyone in the world would argue that Pinterest is evil or bad. It's a site for consuming en masse, plain and simple, and an infinite scroll enhances the experience. Clicking "next" 50 times would significantly ruin the user experience on that (and similar) sites.
pinterest, facebook or twitter are whole-content streams, that's why they benefit from infinite scroll.