The best way to enable Reviews while avoiding bot-spam

• We want to enable the Reviews feature on our site but need to avoid the problems of robot-generated spam. And, since 80% of our sales come from guest accounts, we can't use member accounts as the sole means of verification. So, we're considering two options;
  1. Using the Captcha system which our programmers like, but we're concerned that some of the images being used for matching seem ambiguous.
  2. Requiring guest users to submit their reviews in reply to the email receipt they received in response to their order. That would allow us to verify customers by matching receipts to the records in our system.

  What are your thoughts regarding these two options for collecting reviews while avoiding bots?

Answer:

We actually like Google's Captcha system which, in most cases, requires the reviewer to simply check the box that states I'm not a robot. It's the easiest verification system for real people to use and we find that most bots have trouble with it.

The downside is, if Google suspects they might actually BE a robot, or if they're accessing the site from a suspicious URL, then the (potentially ambiguous) images will pop up. But, if they do, most people will still be able to figure them out while a robot typically will not.

As to the option of matching emailed receipts with incoming reviews, it seems that would also be a viable verification process although quite a bit more cumbersome that having to simply check a box which would otherwise be the case for most people using the Captcha system.

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