When people have something negative to say about you chances are they wont say it in a comment on your website or on one of your social media guest pages. They're going to say it on their own website or an article directory.
With Google Alerts you can stay up to date anytime anyone publishes anything that has your business name in it. All you have to do is enter your business name and Google will email you any time someone mentions you.
You always want to know what people are saying about you or about a product or company that you promote. Think about it, even if you're an affiliate you are a representative for that company. You need to know what people think of the products you promote, thus their reputation is your reputation.
Often times people will be asking questions and by knowing what those questions are you can leverage that by way of blog post or new articles submitted to an article directory. If one person is asking a question it's a good bet that many others are as well.
This works just as well to keep up to date if someone has a negative review on a product or company you promote. You can easily leverage this in a number of ways. Maybe the person has a misconception of the product/company and you can use this on your blog to clear these things up so that people don't get the wrong idea about things.
Another way this can be very helpful is this gives you as an affiliate a very real sense of the customer satisfaction level and how the company treats their customers. The fact is promoting a bad product or a company with a really bad track record for mistreating customers can damage your personal reputation.
Go set up a Google Alert for whatever product(s) or company(s) that effect you and never play guessing games again!