Interesting post...  Here are my thoughts:

(1) I am concerned about the concentration of caches.  Will areas get
oversaturated with caches?  Too many caches in an area can take some of the
fun out.  Imagine a day of visiting public parks in Gilbert and doing 15
caches.  Right now I'll suggest that the SE Valley and the Phoenix Mountain
Preserve have a very high concentration of caches.

(2) Will more geocachers mean more caches are created simply because someone
wants to create a cache.  Will this lead to oversaturation in areas?  I saw
recently that someone I've crossed paths with in another interest has
started geocaching and can't wait to start placing caches.  I suggested to
him that he should wait until he's found 20 or so before hiding one so he
can get a better feel how it works.  I admit the "Where's George" cache that
I placed was placed just to see what placing a cache is like.  I guess this
point gets to the issue of do a lot of "poor" caches get placed just because
people have the cache-placing desire.

(3) I'm concerned about caches being placed in inappropriate places.  The
"Cooked" one in the Phoenix Mountain Preserve is hidden in an area
designated as an archaeological site.  I encountered 2 cache placements this
past weekend in San Diego that were hidden well within areas designated as
"do not enter" due to revegetation efforts (one was even in a county park).
Given that geocaching is governed by those who participate, there needs to
be a clear way to deal with caches that are obviously outside of reasonable
guidelines for placing a cache.  As the hobby grows, there will be more
people involved in the hobby who will not care where they place a cache.

(4) Team Wyle E's 200+ caches is impressive now, but a year or two down the
road there will be many people with 1000+ caches.  I think the number of
caches placed will grow.  I bet Team Wyle E is kept very busy just trying to
catch up with the new caches that are place each week.

(5) Look at the AZ rankings now.  How many people are diehard geocachers?
(Maybe 15-20?)  How many are active but not in a race to find as many as
possible (Probably the majority of  the geocachers.)  People's interest in
things wax and wane.

(6) Personally, my hope that new geocachers will add more creative caches.
I've been in it now for 6 weeks and I have some ideas for creative caches
that I haven't seen yet.  I love the creativity that Team Wyle E has put
into several of their caches.  As the hobby grows, I'd love to see the
challenge revolve around creative caches than quantity of caches.

-Stephen (srdrake)