Your blog articles can be too short when they are 100 words or less. Your blog articles can be too long and that’s usually when they are more than 800 words. See how easy that is?
There are lots of analytical schools of thought that claim Google will rank articles of a certain length and I do believe that is true. Google will rank articles 300 words or more over those lacking in word count. That’s because Google (and other search engines I’m sure tons of people use) assumes that articles with more meat have better content and those with better content are likely more useful and relevant than those that couldn’t even bother to write more than 200 words, I mean C’MON!
So if you’re worried about word count when blogging, I’d say don’t sweat it too much. When you start writing a blog article, consider the following:
Is the subject material interesting and meaty enough for you to write more than 300 words? If so, then do that.
Is the article content going to be plagiarized in any way? If so, then don’t do that.
Is the article SO meaty that there is no possible way to write it in less than 800 words? Consider splitting it into 2 or 3 shorter articles and run a blog series.
As with most of my search engine optimization principles, I tend to err on the side of human conscious and common sense. Write articles that are least 300 words and make them interesting and readable. Optimize your images, add some meta data and blog regularly. Be a human that writes for humans.