Well, there isn’t for most bloggers with commercial intent anyway. See Brians The Two Most Important Words in Blogging:
Itâ€™s certainly ironic that a medium often used as a self-absorbed journaling platform would now need to be overwhelmingly focused on the reader in order to be effective. But if youâ€™re blogging for marketing or public relations purposes, your every post should be purposefully aimed at the needs and wants of others.
Once you realize that deep down we’re all just selfish bastards, it all becomes so much clearer