If VP8 somehow overtakes h264, the value of the author's work on x264 would be diminished. He is the "lead developer" for x264.
This is like having Bill Gates critique a new release of Linux.
Edit: it looks like this article was released a few minutes after Google announcement...
Edit2: it looks like he had access to the spec a few days ago. I still think that Google is not putting their money blindly into VP8 though, they have the money to pay hundreds of analysis like this one and they sure did a lot of them, so it's either good enough or they have plans to make it good soon enough. Still better than x264 for people involved in free/open source like me.
In the comments here, where you might find people discussing e.g., validity, you can find the author commenting on this "issue" further: http://news.ycombinator.com/item?id=1361739
Not to mention an x264 developer is a lot more interested in VP8 succeeding than H264...
If you have any actual concerns, rather than the cargo cult concerns that seem similar to those more intelligent people may voice in situations when they're actually informed on a topic, please mention them.
"Fortunately, it seems I was able to acquire access to the VP8 spec, software, and source a good few days before the official release"