When a blogger writes posts about some products or services, he might be tempted to write about them in a very positive way. While writing about positive aspects is not necessarily a bad thing, I believe that when you are describing a certain product or service, it is important that you also mention any negative aspects that might be important to your readers. What I mean is that you should not recommend certain websites/products that you personally would not be interested in at all. You should try not to be biased and not describe a product only in a positive tone. If you know that for some reason there is something not attractive about a product/service, then do not be afraid to talk about it. I think that doing so will bring you a lot of satisfaction. However, if you do not do so, it might alienate some of your blog readers if they will realize you are not being completely honest. Of course, every writer might have tendencies to be biased in some manner, but it is important to be as objective as possible. This might be especially important if you have a news blog, and your readers are counting on you to be objective.
While many bloggers strive to be objective, the truth is that in some cases it is hard not to be biased. There are very few bloggers who are not biased at all, but nonetheless it is important to try to be as objective as possible.