When it comes to blogging, there are few things as controversial as advertisements.  While there is potential benefit in deriving revenue from "click-throughs" (when a reader clicks an ad on your blog, you get paid a small amount of money), advertisements can be intrusive and damage the credibility of the blogger.  Of the blogs I've written for (including corporate and personal), some have leveraged ads where others have eschewed it.  It really depends on what purpose your blog serves for your small business and the audience you are trying to reach.

It also depends on the type of advertising you host on your blog.  Google's AdSense is one form of advertising that is incredibly easy to insert on your blog - especially if it's hosted on the Blogger platform (as this blog is).  AdSense provides contextual advertising (e.g., relevant to your site's content) through text-based Google AdWords ads.  If you do any sort of Google search, you'll see an example of the contextual ads off to the right of your search results.

You can control where the ads are placed, but that's about it.  You can't determine the content or which ads are posted, nor can you control how much you will get paid for each click-through.  Unless your business relies on peripheral industries to satisfy your customer base, it's probably not the best choice for a small business blog, and would be more likely to turn off your readers!

Another option is direct advertising - leveraging existing relationships - or developing them - with sponsors to deliver content to your readers.  In this instance, you have total control over what is advertised and where it's located on your blog.  It also requires a bit more technical knowledge to have them placed properly on your site.  If the ads are relevant to your business, all the better, as it provides a service to your customers.

A great primer on blog advertising can be found at The 7 Levels of Revenue for your Blog.  Here, they rank the different methods of blog advertising and the potential return you may derive.  Remember, this is only a guide, and it's up to you to determine the best path forward for you and your customers.