I don’t think it’s necessary for bloggers to disclose when they receive free products from a company, unless it is to recognize the company. A blogger would be given free products for a reason and the main one, I would think, would be to advertise the free product you are given on your website. Even if they don’t ask you to advertise them I feel like it’s almost something of common curtesy to mention that they received the product from a certain company and advertise this to their followers. But it’s not necessary, only if it was a condition in getting the product in the first place.
Blogging and journalism are two different things. A blog is more personal to you while journalism is more personal to the audience. Now this can be completely proven wrong if you have a hybrid sort of thing going on, like a journalism blog. But for my purposes I’m going to focus on a personal blog that includes your opinions and theories and journalism which get information out into the world. Sure in journalism you can add a bit of an opinion but you are very limited when you do so and anything you say has to be checked, fact checked, and checked over and over again. With a personal blog I don’t believe you have to be held accountable for fact-checking. You’re not hosting a professional newspaper or journal blog. It’s just your opinion and the way you want to give information out to your audience. If your fact is wrong, the worst thing someone can do is call you out. Again though this only pertains to a blog that is not based on journalism. It depends on the business of your blog.