It's funny, John. I was just asking myself the same question today.
On my Watch List, I have the e-mail preference of "never e-mail me," but I too get the same "review this product" e-mail messages you mention ... and I want to figure out how to fix that.
Do me a favor. Try this fix. Go to your Download.com profile page and select the "My Watch List" tab at the top. (It should be selected by default.)
Also, if that link above doesn't work, click on your username in the upper right corner of any Download.com page to get to your profile.
From the My Watch List tab, scroll down to "Watch List preferences" and look for the checkbox labeled "If available, e-mail me a Resource Guide when I download new software or games."
Is that checkbox selected? If so, uncheck it. Your preference should automatically be saved via Ajax.
After you do that, try to download something and see if you get that "review" e-mail from CNET. The checkbox should turn it off completely. As far as I can tell, there's no way to limit those e-mails to a certain number per week or month.
Unfortunately, if you uncheck that box, you also won't receive any available resource guides for certain products on CNET Download.com, but that might be an acceptable tradeoff for your in-box problem.
I'll talk to Greg (our product manager) about possibly separating those "review" e-mails from the resource guides, since they aren't truly related.
I've noticed that since the overhaul I've also bee receiving e-mails asking me to 'submit my rating' after every time I download a program while logged in. It's become more of an annoyance than a service, as my inbox is set up to verbally announce all new mail. Could an unsubscribe or opt-out option be provided specifically for those feedback requests?