Danno, I think Flickr has some of what you are asking for, but not in a broad folksonomy sense. I can see tags I have made on other’s photos on that photo page.You may want to put these suggestions into Flickr, Stewart and his band of merry developers do a great job of adding requested features and functionality where it makes sense. Flickr has changed incredibly in this past year. One would not even recognize the site from what launched. The do a great job of emergent development that changes based on requests and use patterns.