I found this thread, dead as it may be, via google. I'm resurrecting it to post that the Data Call Enabled checkbox is checked even outside of airplane mode on my Droid.

I checked the Disable at Startup checkbox and then rebooted.

When it came back up, the phone's data was off but the signal indicator showed 4 bars. This appears to be a way to just turn off the data without turning off the voice, which is handy for parents who want to limit their kids' use of the internet on the Droid.