Wow, quite a few opinions and here and I agree with several, both pro and con. My first thought was that I've never paid for anything internet-related other than my ISP so why should I start now... My second thought was that if a user fee of $30/yr would keep those awful pop-up ads away, it'd be worth it.
I'm still ambivalent, but I'm leaning towards coughing up the $$$. We've only found one cache (just *discovered* the game about a month ago) but had a great time and also introduced two other families to the sport. My sister (one of the families that went with us) is now planning on purchasing her own GPS for the sole purpose of geocaching.
One of the main reasons I'd be willing to pay for membership would be the mocaches (I think a new geoterm has been created here). Even though we've only been on one cache hunt (successful BTW), we've already been thinking of hiding our own. Like most, we'd certainly be willing to hide caches that would be accessible to all. But we've also had several interesting cache ideas that we've decided against because of the risk of plunder. I'd love to be able to have complete faith in my fellow man but unfortunately, I've been let down too many times in the past. I'd never hide what I would consider a *junk* cache. But if I'm going to put a considerable amount of time, effort, and yes, $$$ into a cache, I'd like to have a reasonable expectation that it's not going to be stolen or vandalized. I know that the vast majority of geocachers are legit but it only takes one bad apple to ruin a cache not only for the cache-owner, but also for those looking for it after it has vanished or been ruined.
All-in-all $30/yr doesn't seem like an outrageous investment. I've certainly paid more for less.
Hoosiermom - team leader of GeoStars