Google Maps Guide Brianna (highlighted by Barry Schwartz) noted in the new forums that restaurants (and hotels) can add discreet links to menus and reservations. This is done by adding a field with a specific label (either Menus or Reservations) to the Additional Details section of your Places account and inserting the appropriate URL. You can see an example of a linked Additional Detail field in the Place Page listing for Lombardi’s Pizza.
It is unclear how much traffic come from deep in a Places Page. I doubt very much. What is intrigueing is that now we might be able to tell. It will be a simple matter to create a vanity url for the reservations and menu pages that will track the local traffic that is being sent.
Obviously the Additional Details fields support a number of phrases that trigger the distinct links. I wonder what other specific tags might also trigger the results?