but I don't think you'd need such powerful server to serve ads. Maybe having two or three smaller servers (and using them based on the visitors location) plus a proxy server would have been cheaper and more efficient. Also, were you ever able to try alternative web server software such as nginx, which is usually lightweight even under heavy load?
Some time ago I tried to test CoinURL on the node where Peerbet is now located (XEN with 2 CPUs). This server is well-configured by professional admins. CoinURL's response time here was acceptable, although I am not sure even this node could be able to handle current load.
Have you thought on scaling back CoinURL to be just URL shortening with interstitial advertising like in the beginning, and dropping the banner ad portion of the service (not sure how much that would help reduce the load)?
Interstitial ads are too cheap and requires too my personal time to review clicks, that it is just not worth.
I read your post but I'm not sure I understand what happened to the balances of the user accounts. Is this money gone? Is it included in the "unspent clicks and impressions" category? I speak for my ~0.05 btc so it isn't much of a loss (well, if you take into account that's how much I get from ads in two months, yes it's a big loss) but I understand there may be people who had higher balances.
Publishers can make a withdrawal of the remaining funds, advertisers can transfer ads to my other sites.