Please correct me if I'm wrong, but from what I understand, when you enter information on the Geocaching.com web site, you effectively transfer the rights to that information to Geocaching.com, at which point you no longer have the rights to that data. You can only use the data 'internally' at that point, and cannot share it with anyone publically.
Geocaching.com however, can sell, rent, or lease that data - the data you gave them - as they wish.
So as I understand it, by submitting your data to Geocaching.com you give it up, though if you submitted somewhere else first, I think you would retain the rights to *that version* of the data. So pretend you first enter info about a cache on Geocaching.com, then mention it on a mailing list, or on your own web site, you would be in violation of the agreement.
For the people that submit their data directly to Geocaching.com first, does it bother you that they take away your ability to use your own data?