Well, yes and no, Geezer, two issues here.
Some of their caches have been archived - meaning that the area is clear and new caches can be placed there.
The second issue is active caches that are being found but the owners are gone or unresponsive.
As long as the cache is in decent shape with no issues I will generally leave it alone and it becomes "community maintained"; we have a number of caches that are pretty neat but the owners moved or dropped out long ago. Rather than have a good cache archived finders keep the level of trade items up, replace full logs and so on.
Once a few DNFs are logged, or someone wants to use the area for a new cache, or maintenance is a problem, someone can do one of two things:
File an SBA - We take Should Be Archived notes seriously, and a lack of timely response by an owner will almost certainly get a cache archived.
Adopt it - if someone desires to adopt an abandoned cache they should contact the owner and ask to adopt it. If the owner wishes to let this happen they must go to www.geocaching.com/adopt (http://www.geocaching.com/adopt) and enter the cache ID and new owner's name to complete the adoption. No Reviewer need be involved in an adoption.
In certain circumstances someone will want to adopt a particular cache and the owner can't be found. In this case write a note fully explaining the situation to [email protected]
and they may decide to do an administrative transfer of ownership. That decision is based mostly on the percieved value of the cache (log history) and the maintenance track record of the adopting cacher.
Hope that helps,