Mildly, but less so when you consider that it's a blog not a product. And even less so when you consider it likely fell over due to load and didn't silently delete the blog data.
It's a different kettle of fish when there's writes; but for reads, it should be a walk through the park.
This comes up every time a blog falls over that discusses or criticizes a database on HN and it's just as shallow as it ever was. Do we really expect anyone to spend significant time optimizing their blogs for load that may not ever come? We talk about "pre-optimization" and "core competency" routinely on here and then shoot the messenger when a wordpress blog using MySQL falls over that's criticizing something like MongoDB. It's irrelevant to the point of silliness.