I dismissed HistoryPin the first time I saw it as "not useful." The site is designed as a visual map. In theory, you or another group should be able to upload historic images. Someone could then search for a location on the map and look at all the images. The first time I examined the site, most of the images were family snapshots - not of much interest to anyone outside the family. However, that's starting to change.
Thanks to increased usage, HistoryPin.com is starting to develop. There are now vintage home photos up alongside the 1970s snapshots. It's still thin the small towns, but the promise is there... Now if I can just convince enough Luxembourger towns to add images!