Just wanted to add a data point out there in case some one else searches for this.
Last night my Droid wouldn't recharge. That is, the "plug" didn't appear over the battery icon and the little white LED on the USB port didn't light. I was tired and didn't worry about it, but left it plugged in overnight.
This morning, I woke up and the phone was still at 15% power. I tried plugging it in to various outlets, my laptop, using a different cable, etc, but could not get the Droid to charge. I also noticed that the battery icon now had a question mark over it at all times. Also, neither of my laptops would recognize the droid anymore - both said "USB device has malfunctioned".
I decided to bring it back to VZW late this morning. They tried swapping batteries, but the battery icon still had the question mark on it even after multiple reboots. After quickly looking on-line for any hints, they decided to swap it out for a new unit. I was back up and running in about 30 minutes.
The tech there said he thought it was the (internal) power supply. Dunno what he based this on, but I got a new Droid, so I was cool with it.
Again, just wanted to share my experience.