What about fake reviews that are posted by the competition. I have a hard time believing that anybody that is posting fake reviews of their products isn't doing that for their competition as well.

Ultimately, I tend to look for the reviews that are the most informative, things that look plausible and give me more information than what's in the listing. Usually those are fairly reliable as they're harder to fake. Not that it's a perfect system, but it is more time consuming to post a review like that since you really have to do different ones for different sites.

If I was being to paid to astroturf a product, I'd prepare a number of generally positive and a few 'negative' reviews that pointed out a few flaws in the product. Of course those would only be flaws that the majority of people will either not care about, or will see as positive to themselves. The idea is to seed a small element of trust in the product, and take away the feeling of blind risk from the potential customer.

In some of those reviews I'd also mention another product or two that I felt were 'better', again only in some specific way that most people wouldn't care about. This seeds an element of legitimacy to the product, especially when comparing it against known good competition. The idea is not to get 100% of people thinking your product is the best, but to catch a large number of customers that would have otherwise never even considered your product.

The third sneaky thing that I'd do would be to review a competing product or two with a very minor mention of the product I'm being paid to astroturf. In that review I'd be generally positive, while at the same time throwing in a few questions that seeded some doubt and uncertainty about some seemingly important aspect of the competitor's product that my actual product reviews (and legitimate advertisements) had covered as being fully supported. In this way, the person 'researching' the general class of product is likely to do some further research into 'my' products - specifically searching for these 'missing' or 'doubtful' aspects that I've alluded to.

The above tactics are readily seen across the board in general advertisements where a company will harp on about some new 'feature' that they have - especially a feature that competing products don't officially advertise or mention - thus implying that the feature does not (or may not) exist in those other products. In reality the feature is a straw man style argument that compares apples/oranges in a way that less than 10% of the potential market would see as an invalid or incomplete comparison.

How does anyone know that there aren't people out there readily using any or all of the above tactics?