duplicate photos without impacting storage

i have lots of photos and videos that belong to multiple hierarchies.  for example if i'm on a trip and i record video of some concerts i'm at, i save those videos to a 'travel' folder organized by place and date and also to a music folder organized by the band i'm recording.  this is really handy as i can share the entire history of footage i have of that band with someone easily by sharing the the band folder and i don't have to wade through the other videos/pictures from the trip. 

ideally, i could do this without impacting storage.  after all, it is the same photo or video, and under the hood dropbox could just have two different pointers to the same video and i could share one pointer without sharing the other, thus not doubling the storage space.  i think this would be useful for a lot of users!