Would love to add some stats around the following:
How many different finders have also found the caches I have found. I find a single cache and A,B & C all find that cache. Then my finders in common would be 3. But I cant just add up all the caches I have found and their number of finds because on cache #2 B,C & D are the only other finders - but my in common count is now only 4, because B&C already shared a cache in common with me.
Yes Map Compare will do this for 1 person, but not at any scale, I simply cant get this number without hours of work. The finders in common data would help map the community of cachers.
This is potentially a very deep vein of fun data that can be created.
Some things you could do with this...
Count finders from other countries or states in common. I love looking at the website plugin that shows how many people from different countries have found each cache, and often wonder how much "international exposure" I have from my found caches. When I am planning trips and I see a cache with lots of international visitors it automatically gets added to my planning queue.
Work towards a 7 degrees of separation for geocachers - what is outlined above is just the 1st degree - people who have found caches you have found. You could take it further and find how many people have found caches that the people you have in common have found would be 2nd degree and so on. One nice thing about this stat, is that every day your people in common should grow as you find caches or as others find caches you have found. That means your distance to the average geocacher would shrink over time through the finds of others.
Seek out "endangered cachers" whose finds in common may not be possible once certain caches are archived. Extinct cachers would be those who every cache they have found is now archived - likely cachers who no longer cache. This would encourage cachers to keep older caches alive and perform maintenance on them - and give another reason to get out and cache.
Get lists of "in common" cachers - how many people do you have 20/50/100 finds in common with. Some will be locals you already know, others might also be county hunters or terrain junkies or those who boat and cache or earthcache enthusiasts or cemetery cachers or any number of other ways people cachethus without knowing it you are sharing lots of the same experiences with them.
With just these few ideas lots of new challenges (formal and informal) and reasons to seek out specific caches would get created - for me I find my enjoyment of our sport goes way up when I have challenges like these to visit random caches that I might otherwise not have visited.
I could envision challenges where the goal would be to have finds in common with 100,000 or 1 million other cachers, challenges to have cachers in common from 50 different countries, 10 caches in common from 10 countries, 100 distinct cachers in common from Finland, challenges to find in common half the active geocachers from your state or country, find 5 caches in common in 10 different states with another cacher or find 100 caches in common with 1 person etc.
If this was to catch on as a metric people seek out, it would potentially create a need for lots of new search tools, which from a developers perspective allows them to put simple tools out for free, with advanced functionality behind a subscription wall. I was one of the original donors to this site before subscriptions got formalized and I have stayed because of the tools you provide that allow me to cache in fun and unique ways not supported by Groundspeak, I think data like this might help others find a reason to also be a paying member.
To start I think I would eliminate the complexity of the above and focus on how many "cachers with common finds" someone has and start displaying that and see if that leads to other requests for tools around that concept.
