Thank you for sticking with this. I read several of the Google articles and one, somewhat involved and technical article claims it can "sort of" be done but ends the article with "I have not tested what happens when multiple users access / attempt to update Picasa at the same time, but I assume it’s not a very good idea. We’re ‘cheating’ here, Picasa was not designed to work in a multi-user environment, so let’s plat safe: only one computer and one user should access it any one time." Kind of a deal breaker. 
Here's another update. Light Room is an amazing program but after tagging thousands of images I realized that it's not touching the metadata in the files at all. It's keeping that tag info in its own proprietary database in a separate location. That would be fine for a single photographer business but if it leaves the images un-tagged and I am the only one who has the capability of searching, that kind of defeats the purpose of using Light Room too. I think next I want to experiment with Thumbs+. It seems kind of promising, but we'll see.
