My wife and I own a Droid and we both had a similar issue today. And it's not like our phone came from the same batch as I purchased my Droid in November and she purchased hers in February.
Today, I literally watched my battery life suck down from full life to no life in a matter of a couple of hours. I was working today, so I did not have a chance to charge it until this afternoon. As I was driving home and had the phone plugged in, it would not turn on. I really don't know what was wrong. I thought maybe it was the power button because I pulled the battery and memory card several times while driving down the road and was still getting no response.
After thirty minutes I was finally able to turn my Droid on with low battery life. I get home and plug it into the wall and it is fully charged now. My wife comes home from the gym and tells me the same exact story about her phone. I was perplexed.
Any ideas how the same thing could happen to two different phones on the same day?