I don't think its MFA because its obviously useful. However, I think he's wasting his time because most people who want to check PR (who even know about PR) are webmaster who can spot an add a mile off and avoid it! Good luck to him though. DoA
The 'useful content' is after you use the site submit button, therefore he won't get banned but will (I think) have a lousy CTR
Will the google bot enter a url and click the submit button to get to the 'useful content'? I think not! He's also using 4 ad units but the tos says only 3 per page. I think his running the risk of some form of penalty as Google doesn't like MFAs.
nope your allowed 3 ad units and one link. Also if you have four ad units on your page, only three will usually display anyway, unless you try some other trick. As for the site, looks like they are skating on thin ice.
You are allowed 3 ad units, and THREE link units - http://www.searchenginejournal.com/adsense-policy-update-now-allows-3-link-units/5050/
Oh that site yells at you "get out! spammage!" It looks worse than those default domain holder ad pages..