As someone who worked through the transition from print to blogs, I remember the day Gamasutra switched from referring to us as "consumer blog" to "news site," so I know better than most the fluidity of perception. Our rules (here's Joystiq's ethics policy) are pretty clear, and that's thanks to years of relentless scrutiny and near-daily accusations of being paid off.
Here's some questions, for those watching YouTubers: do you even care about disclosure? Legal issues aside, do you think there needs to be some kind of generally accepted rules? In your opinion (since perception is key here), are you viewing them as authoritative figures giving transparent opinion on video or are they paid entertainers?