I discovered quite by accident that wpdbspringclean does not work correctly on multi-site installations, and now I have a demolished database. Unfortunately, my automated backup was not activated and so I am unable to restore the database to the form it was in before this plugin literally gutted my site of around 15 or so sub-sites.
I can accept that I should have taken extra measures in advance to ensure the database was backed up, however I also fault the documentation for this plugin for failing to mention incompatibility with multi-site configurations. I had previously had excellent success from this plugin on a single site and so I felt confident based on experience that it wouldn't be a problem.
Please update the documentation to make strong warning against use of this plugin on multisite installations, because it tends to destroy all of the subsites and leaves the main site in a nearly unrecoverable condition.
As it is, I'm now going to have to rebuild my site from scratch.
Now, as I say, I don't fault anyone but myself for not performing a backup prior to using a plugin that I had seen work without issue in the past... I had what I believed was good reason for not wasting time on that, and it turned out I was wrong. But to help others avoid this, it would be prudent to update the documentation to mention this.