Cache proximity
From GeoWiki
Within geocaching circles it is generally considered good practice to hide your cache in a location that is not too near another players existing cache.
On geocaching.com this is enforced by reviewers but on GCA this is a purley voluntary process
To facilitate this and to ensure good karma on your behalf, we provide a proximity warning if you place a cache within 150m of an existing cache (be it gc or gca).
This is purely a courtesy, it is up to you as to if you decide to move it a bit or not!