I seem to be having the same issue with OnBeforeWrite. Still no conclusion?

No.. I ended up taking a different route. I'd really like an answer as to why these functions get run so many times. I really screws things up for me.

Just a thought, don't have time to test right now, but does this only happen on SiteTree objects (ie VERSIONED?).

I wonder if versioned is causing onBeforeWrite to happen multiple times as they're written to different stages.

Would be easy to test - if it happens to a page, but not a standard dataobject, it would would probably be the cause. Then extend the data object with versioned and see what happens.

I have a strong feeling that onBeforeWrite and onAfterWrite run once for every object relation. My class had two has_ones and a has_many, and I believe i was getting 4 writes. One for the main table and 3 for the relations... ??