Why do the buttons on my Incredible occasionally light up? I've noticed that sometimes the four buttons at the bottom of my HTC Incredible sometimes light up for a couple seconds at a time, even when the phone is just sitting unused on my desk.  Until now I've attributed this to a software bug, but I recently noticed it doing this while I was digging around in my email on my computer.

Does this indicate data transfer?  Or does it have some other significance?
You phone should light up when you activate it. 

When an internal process either stops or wakes up you phone (like you said to start data transfer) or on other actions the lights can light up.

When a process crashes my phone lights up the control keys too, usually with a buzz.