Clip Power Question

Ok, this question may seem a bit odd, but here it goes.

I discovered once, when I shut my computer down, that several things happened:

1 - The computer’s USB port remained powered, and my Clip continued to charge.

2 - Though the Clip was still connected, since there was no data signal from the PC, the Clip could play.

When I discovered this, I purchased a USB wall charger (a power brick that plugs into the wall, that has a usb port for charging) so I could plug my clip into my reciever and use it there.

My question is: when playing in the above state, where is the player drawing power from, the battery or the USB port?

the USB port and it will trickle charge if the battery is full. 

I have heard that trickle charging a Li-Ion battery is bad, is this correct (assuming I’m correct and the Clip has a Li-Ion battery)?

lithium polymer battery and no trickle charge will not hurt it.