[whpalmer4]

Rebuilding the database doesn't change the need to keep a transaction trail for any devices/clients which aren't fully up to sync, and that transaction tail (stored as many little zip files in the package) is what causes the database file to swell.

If you cause all your devices/clients to be synchronized now, and repeat that operation again in an hour, you should get more compaction. If you are in the habit of only having OmniFocus open in one place at a time, your database may tend to stay larger because of this, and there will be more times when a larger amount of work needs to be done in a sync. The sync code allows up to an hour for a slow client to go through the motions, so the two complete syncs an hour apart will squash the transaction trail down to minimal size. If you do a Show Package Contents view in the Finder on the OmniFocus.ofocus file, you can see the dates on all the component files and see how the compaction takes place.