How many times you go to a museum, see a painting and wanted to express your opinion about it? How many times you go to a new restaurant, have a good dinner and wanted to leave a good comment about the chef? How many times you enjoy your night in that new pub and wanted to say this in public and not just to your friends. How many times you are in a physical place and wanted to know what are the nice places to see in the nearby, and wanted read the opinions of the people who have been there before?
Imagine a mashup between Bing (or Google) Maps and Facebook Wall. You can attach a Wall to any physical location in the map and you can immediately start commenting and leave your opinion in these walls. You go to see a movie and you can get the comments of the people who have been in the cinema before, and leave yours if you like. You just want to find good places for an hangout, well you take your mobile and the map will suggest where to go given the experiences of past people. Anyone, not just your already known friends.
This will be an extension of current Facebook Wall.
This is my current playground project. Reattach Walls to physical locations, and give the opportunity to different people to get in touch just because they share an experience in place and not because they are already friends. They don't need to be there at the same time, they just need to share the place.