Single page application? Can you explain why the existence of next/prev relationships would break these? I would expect such a site to simply not use this. It's definitely nice for linearly-linked content on supporting browsers (e.g. old opera, as mentioned elwewhere in this thread).
Well, look at it this way, when creating a SPA, you're running everything in a single place. A single HTML page. In some instances, it makes sense to push the state to the query string, but often it doesn't, and more often still are the occasions developers haven't thought about it. So every time you hit the back button, and weren't where you thought you would be, that's the same issue. SPA frameworks's are getting better at that, but this still happens to me on the daily.
