In short, there are two types of advertisers on Cnet.

1.) Direct - Advertisers purchase ad space Cnet sells directly, and the Cent advertising team inspects/approves each ad individually. In the past 5 years, I can only recall two problems, both of which were corrected within a few hours.

2.) Google Syndication - Text ads provided directly by Google. Cnet applies filters to omit known-bad ads, but does not get to investigate/approve each one individually and Google is extremely lax in policing their own ads. Thus, they -- unfortunately -- often contain links to fraudulent and borderline companies/offers.

Thankfully, Cnet remains one of the more trustworthy sites for news, downloads, etc. Nevertheless, the latter is hard to avoid, as Google, Yahoo, Microsoft, Cnet/CBS, and hundreds of other top companies all use Google Syndication. Thus, I always recommend using an ad blocker, such as AdBlockPlus for Firefox, and exercising caution when following such links, especially those from Google.

Regards,
John