So, this sentence is correct: "Sagt mal, was ist eigentlich der Sinn hinter Clint Adams blog?!" (or as I would rather say "... Clint Adams seinem blog?!" :). And, so Clint is right.
Update: I was notified by two different people already that the current new german grammer disagrees with me. http://www.ids-mannheim.de/reform/regelwerk.pdf tells in §96 that the usage of the apostrophe is right. Well, of course I'm conservative and haven't upgraded to the new grammer. Besides of that, my feeling is still that the apostrophe is wrong.
Another nit-pick: The "... Clint Adams seinem blog"-style is known to be not official german. But it works quite well, and is even conformant to the new rules.