Inspired by / corrolary of : previous HB idea (linked below). But doable with today's technology (no magic).
Many many folks upload photos to http://ophoto, snapfish, or other websites. When doing so, they could be presented with a checkbox to "make these public" (off by default). Make it easy,
while they're uploading them for their fam/friends, but still default the choice to "private".
Allow them to enter meta-data on the photos (location, date/time).
Then, when you get back from your vacation in XYZ, you goto the site, and can search for other photos of the area on those days you were there. Missed that rainbow? Street juggler? Too embarassed to take a photo of fabulous random thing? Even wanting to go back there, and looking for ideas of neat things to see & do? Someone else took those photos and you can view & copy them.
Some of this metadata could be stored in the JPG file, and if it catches on, you could develop cameras that could embed GPS coordinates into the meta data.
Allow anyone to rate your photos on a few scales (originality=2, image quality=4,funny=0,etc) so that when the database gets big, you can filter out the best ones.
The site could easily be funded by relevant advertisements for things in those locations / seasons.