No, interest is not paid from new deposits. When you withdraw the coins may have came from someone who deposited - coins are coins, but we don't operate a ponzi scheme.

Like I already said, we do quite a few very short term (week or two) loans where it's 62% APR (assuming full usage).

I do invest in ASICMINER, but that's not everything. The current situation is that even if I lose an amount of BTC or assets equal to our current liability, I can still pay everyone back. The question comes down to trust, and you need to make your own judgment on that