At its heart, it is a conflict of interest and a clear violation of traditional journalistic ethics. At the very least, it is contrary to what one might assume to be a societal norm. Once one is aware of what they're doing, one feels taken advantage of and that is simply not acceptable.
No, it's just not a good look for a news organization to have content so entangled with income, especially if they don't even mention it. I think http://thewirecutter.com/ does a good job, and they're also way more open about the fact that the site is covered in affiliate links.