Using the imperative is like voicing a command. Spare use grabs attention. Overuse slides into the dictatorial.
--Bruce Ross-Larson, Effective Writing
Using the imperative isn't like voicing a command, it is voicing a command. And this author is correct: it grabs readers' attention only if used sparingly.
Two examples from my food blog Casual Kitchen:
1) Never mind that the days of the standard grocery store dominating the consumer landscape are nearly over.
2) Your grocery store can charge whatever it wants for the products it sells. Please, don't bother getting angry about this--just accept it.
A side note for readers interested in learning about logical fallacies. The second sentence is an excellent example of the "proof by vigorous assertion" fallacy. Hey, I screw up sometimes too.