It is best not to get onto services like CNET when their systems don't let you unsubscribe.
Be careful when subscribing to sites requesting your email address. Some are annoying like CNET, but others I've heard from have experience unwanted spam which have meant they've had to change their email address.
In this case I'll end up discarding the unwanted emails at the mail server. An action that shouldn't be required but that's all part of being part of an internet connected community.