I was a part of Betowess' thread on this topic the last time it was dicussed. Since I started actually paying attention to it, I have observed that every time I introduce a new piece of driftwood into my rubbermaid soak tub, I get this film on all of the pieces no matter how long they have/had been soaking. After a few days I remove this film and it never comes back, well, at least until I introduce new wild driftwood into my soak bucket.
I haven't added a new piece of driftwood directly into a tank that I can recall, so maybe this isn't help to you, but I haven't had any post-problems with fish/shrimp/plants that I can remember.
When I was trying to figure out a root-cause of it all, I didn't get very far in my research. I did find my observations on the internet of people saying that weird parts of their tanks got covered (substrate areas, certains rocks, plants, etc). I didn't read any accounts of any actual health problems though.
I am not sure if this is helpful or not, but just figured I'd share what I found... is-all