I have had my Droid replaced... ready for this?... SEVEN times because of this issue. That's right, my warranty has covered Verizon sending me SEVEN new Droids (meaning 8 Droids in total - 9 if you count the other time I had it replaced because one of the refurbished units' microphone didn't work).
Verizon got rid of their multi-FRU policy, so they won't replace your phone with a new model, ever. They will just send you the same phone with the same problem 100000000 times. Literally. Whenever mine needs replaced, I call them and they say "yep, you have no other options unless you want to upgrade to the Incredible" - and I say "Why bother? Not like it will ship any time soon" - to which their reply is usually no response (because I'm correct) lol.
The headphone jack on the Droid is a joke. If the Droid X is plagued with the same problem I'll trade in my motorola phone(s) for HTC, even if HTC makes cheap plasticky stuff.
By the way, my headphone jack is AGAIN failing (crackling and pausing randomly when it gets SLIGHTLY wiggled) and if the Droid X weren't launching so soon, I'd be totally getting it replaced again, lol.
Good luck to anyone using the Droid's headphone jack... it's complete and utter crap.