Include ads sparingly in a blog post or article when the topic is more general. However, don't do so if you're trying to sell something like a product or service because it's just not ethical to disguise advertising as content. If you’re piggy-backing on sites that were written by somebody else and have keywords targeted for your goods and services, this is considered "passive" personalization (which some people may call “hijacking”). There are plenty of companies who find themselves needing true integration with existing information like fonts, images, colors, and logos to be able to share their message in an identity-preserving manner – without impinging upon someone else’s hard work.