Maciej Cegłowski will be using a large pool of Pinboard’s bookmarks to gather data on link rot, and I’m pretty excited for the results. I know of things I’ve bookmarked from just a couple of months ago that have already been moved, and things that I’ve bookmarked from ten or more years ago that are still around at the same link. My own anecdotal evidence suggests that links from 2007-2011 or so are frequently rotted, probably due to rapid changes in site architecture best practices during that timeframe.
This post also illustrates how to research user data without being a dick about it. Cegłowski is upfront, is going to ensure that links are not associated with user names, and is offering a clear, simple way to opt out.