Put advertisement but make sure that your blog visitor doesn't get irritated when ads pop up one after another like a flood.
Search engines don't spare any blogger. E-commerce bloggers must keep in mind the search engines in mind while writing blog posts. SEO friendly writing improves the search of your blog content.
E-commerce bloggers must carefully write keeping their audience in mind. Everything you post on your blog will speak for your product or service. Your interaction with bloggers in comments and otherwise will give you a direction.