I read two security buttetins that should be considered for Watchtower:
Opera server breach incident
In this article they wrote: "Earlier this week, we detected signs of an attack where access was gained to the Opera sync system".
They also wrote: "we have reset all the Opera sync account passwords as a precaution".
Dropbox Password Reset Required
In the article you can read that "users who Signed up to use Dropbox before mid-2012, and Have not changed their password since mid-2012" must Change their passwords.
I think both issues should be added to Watchtower.