Simply put, you may lose your data. Fortunately there’s a very detailed solution for it:
If you are using CouchDB 1.0.0 and have the default setting for ‘delayed_commits’ (true) then you are affected by this data loss bug.
For current users, these instructions will ensure your data is safe. First: do not restart your CouchDB!
The bug doesn’t affect previous CouchDB releases.
CouchDB 1.0: Critical Bug Found, Fix Available originally posted on the NoSQL blog: myNoSQL