I just found out. Props to Steve Sandells from wotZcool.com for sending me a message about it.
It looks like the same folks who hacked him last time are up to it again.
This time they were being a bit trickier by loading junk in iframes in the background while leaving john's actual content up and running.
This results in a very slow load time but, otherwise the site looks as it normaly does.
I contacted John but he already knew.
Last time this happened he had to pull his blog down for almost a day and plug the hole that was exploited. Hopefully he'll get this new hole fixed soon!
If you do visit John's blog JohnChow.com be sure to blast out your cookies and what-not. You don't know what might be lurking there after the hackers strike!