Oh, no! Susan, does this mean you're not going to read my blog anymore?
Seriously, without knowing what this little test takes into account, I'm not putting much stock in it. True readability assessments are based on much more than just vocabulary. If this one considers nothing more than that, I could easily envision a blog that is incoherently written and riddled with poor sentence structure nevertheless scoring at a high reading level simply due to the presence of a few big words. Conversely, I think it's possible to use "big words" in a reader-friendly way, defining them either explicitly or through context.
Still, this was a fun diversion. For some reason I couldn't make the link above live, so if you'd like to run this test on your own blog, click here.