However, I think that many of us would love to see specific examples of "caches only 300' apart". I certainly don't know of any, and I have had caches turned down that were 524' from another (to use Keystone's example).
OK, so the example I cited when I posted this was flawed because I failed to notice that one of the caches in the parking lot example had been archived. But if there are those who need to see specific examples - here's another I recently encountered. Check out Bob's Sinkhole and Beach Vacation TB Hotel. By my measurement these two caches are 108' apart. No big deal you say - well now do a search on caches named Patsy Pond # . You will see that, including the two aforementioned caches, there are a total of seventeen caches all within a 0.2 square mile area here. Total (route)distance between all of them is about 2.1 miles, and this is in a wilderness area. Please feel free to correct me if my software has calculated this improperly, but what I'm getting at is that there definitely are places where there exist a heavy saturation of caches. Note that I am not making any judgements about any of the named caches - I'm just using them as an example of cache density.