How can any person of sense think that they can blog about their place of employment and not get fired? Sometimes the fact that common sense does not exist for so many people just bewilders me.
It seems obvious to me that you just should not blog about your employer. As an employee you know things that no member of the public would know. What average customer or even a journalist is going to know about the attitudes and behaviors of your boss and co-workers? Even if you only choose to blog about public announcements, you'll end up adding your two cents worth about how you know that this "isn't true"/"won't happen"/and so on.
If you blog about products/services that your company offers then you clearly have more information than the average consumer. The consumer may like to know what you think, but he'd really like to have such information from your company and all their competitors so that he'd have perfect information. As the consumer's unlikely to get the competitors' inside tips, all you're doing is undermining your employer.
Obviously, the best option is to blog away about anything you like other than your place of employment, but some people just love to show how "clever" they are.