Why not! Most of the websites or blogs have advertising on it. So, why shouldn't you! If you don't exagerate, like some websites do, it's not notable. Advertising even motivates you to write a new post. You might get some visitors for that post, and get some revenue for it.
Why do you blog?
Think about the reason that you write regularly a new blog post. Is it because you really want to share you're knowledge? But for wat reason you want to share it! To be an authority in you niche? And if you...