As with any pursuit in life, plateaus are often common and a fairly natural occurrence. Things that make the difference between hitting a plateau and overcoming that plateau are often the tactfulness of the approach and the wisdom to put one's cards in the proper place. In the world of blogging, the rules, in many cases, are no different.
Many bloggers are commonly plagued by the dreaded plateau in readership. Even if your blog is unique and interesting, it might eventually attain a readership level that remains at a certain level and becomes extremely difficult to improve upon.