Granted I'm still a newbie, but my personal feeling is that a cache should be placed for the location (i.e. scenic view or unique natural phenomenon, i.e. I've Found My Thrill cache, Barred Island . . . almost cache), historical aspect (i.e. Before Lizzie Borden cache, Boxboard Mill cache) or in a spot with special meaning (i.e. Out of the Ashes.)
Maybe my thinking is a bit off here, but I a) try to put some thought into my locations of my caches, b) I try to give some thought as to how I want to place the hide (i.e. any special camouflage), c) I try to make my signature items unique and personal so that folks will realize that I took some time and energy into creating them, d) the items that I place in my caches and trade are in good condition and do not look like I found them at an old dump site and e) I have made a personal resolve to try to set out a cache for every 25 found caches as one way of "giving" back to this activity. As I said, these are my own personal views and are not meant to be a sleight to anyone who does not share these beliefs.
Unlike some folks I am not adverse to micro caches as long as they're done for a real and meaningful purpose at a location where it is impossible or nearly impossible to have a traditional cache . . . and like most of you folks (although I've found it) . . . finding a 35 mm canister under a lamp post in a fast food restaurant parking lot or attached to a guard rail of a donut shop doesn't exactly give me the same thrill say as the scenery at Oak Point cache for example.) A good example is a cache at a memorial in Detroit . . . a quick and simple find. The cache could have done a virtual cache but instead chose a micro and I think it worked in this case as the area involved was in a small area. Again, only my personal feelings.
As for the numbers . . . I truly don't believe it's all about the numbers. I suppose some folks might get a certain thrill of being one of the top leaders in finding caches or being the FTF, but for the short time I've been caching it's been more about the thrill of finding the cache (not necessarily what's inside, but it is nice to find a good trade item once and awhile) and the thrill in discovering new locations.
Finally, getting back to the original question. I personally believe that if there is an area that is worth putting a cache (once again due to its unique location, historical aspect or personal reason) I would not be adverse to any limits . . . as long as folks don't place caches out there just for the sake of placing a cache and as long as caches aren't so close to each other that it gets to the point where you can simply go to a parking lot and check under each lamp post or scan the nearby guard rails or find a cache and be unsure as to whether the found cache was the one you were searching for or another located close by.
"Courage is not the absence of fear, but the realization that there is something more important than fear."
"Death is only one of many ways to die."