It's an arms race. Advertisers may be able to detect ad blockers in the short term, but eventually they will lose. That's because users control their machines and advertisers don't. Widespread use of adblock-blockers will only hasten this inevitable defeat.

The techniques used by the project to which you've linked can be trivially worked around by detecting the script itself and either not running it or telling it what it wants to hear. (Come on: an iframe? You really don't think a browser extension could lie about that? I expected at least some kind of server-client traffic correlation for a serious ad-blocker-blocker attempt.)

Just clicked the demo http://www.lavancier.com/adblock/ and: "Ads are enabled in this browser. :)"

Now guess if I block ads?

Except this will be blocked by script blockers such as noscript which used to #1 most downloaded extension for firefox.