There is a very eccentric and yet fascinating blog in Japanese about the daily changes made to a specific Japanese vending machine. Only the title of the blog is in Japanese, all the rest is shown through daily pictures of the vending machine. Most days there are no changes, but once every 10 days or so, certain drinks are replaced by new offerings. With this daily record, it is easy to see that these changes and the placement of the drinks is not random. Worth a look.
I first became aware of this blog through Neil Duckett's blog.