They tend to be not so knowledgable. Whether they are very biased is hard to say, they tend to be a bit biased when it is about certain computer makes or so... they rely heavily on advertisement and at times I have the idea that shows.
Canon EOS 350D, Tamron SP AF 90mm F/2.8 macro, Sigma 18-50mm F2.8 DC EX, Canon EF 70-200mm f/4 L USM, Tokina AT-X124 Pro 12-24mm F4, Soligor 1.7x C/D4 DG Teleconvertor, Manfrotto 724B tripod, Canon Powershot S30
From what I see at CNET on cameras, they tend to look at overall technical specs for the price, but don't ad much comment to user friendliness or photographers choice. My boyfriend just wants to press one button and likes his equipment to do all the thinking for him. (He dosn't want to learn specifics, or do alot of research so he likes CNET). Sony tends to be rated high, but gives very little control for a camera buff.
CNET has to cover a lot of ground, so it's natural that they can't do even 10% of the job that a dedicated reviews site would. They're a good one-stop shop if you don't want to blow hours off on careful research, and for really casual users, I don't see anything wrong with using CNET (however, I'd steer clear of PC Mag and PC World). You just have to be careful to know how the CNET rating system works (a 7/10 and 8/10 is considered very good, and even a 6/10 is OK) and how they weight different pros and cons.
If there are any biases (I personally don't see anything that I'd truly consider a "bias"), I would say that they favor Canon and Sony and tend to downplay Nikon and Panasonic.
Careful with Cnet, I use it to find out what's new on the market.
The User reviews are usually pretty good. Some products have design flaws, if they do someone will be bitching
So, I would not recommend to use cnet.com exclusively.