In fact, many blog posts that I happen along are quite short. The main key is: does the blog post convey a message of deeper significance? If it does, and the user and the blogger connect, than the blogger can be forgiven their brevity.
All in all, though, it’s rare that a completely short blog post will convey enough meaning. If you feel your original thoughts aren’t clearly outlined, then don’t hesistate to add a few more sentences, or even a paragraph to make clear your meaning to any readers who happen by.
With practice, you’ll easily be able to determine just the right post length for every occasion.