Dropbox, a file-synchronization service, used to post detailed release notes for its software updates. Here's the last such set of notes, posted on 11 March 2016:

New in 3.16.1
* Small fixes
New in the 3.16 series
* Dropbox badge fixes for Office 2016 compatibility
* Many small fixes and improvements

And here's what Dropbox has been posting for releases since then:

Thanks for using Dropbox! The desktop client is regularly updated with many improvements and fixes.

This is as good as posting no release notes at all.

We'd like to see Dropbox return to posting detailed release notes for every release, so that users can see and take advantage of new features of interest, and make informed decisions about whether to upgrade or continue using the service.