The "review site" model has been popular for a many years, and for great reason - it's one of the most effective ways of translating Internet traffic into commercial value (sales). Review sites - done well - can bring in as much as $5k a month purely on autopilot.
The problem - however - is that most people have absolutely no idea as to how to make a review site work effectively. They typically make a very low quality system which essentially prevents them from making any major growth. As a consequence, they give up without having really found how to make the most of the technique.
The biggest mistake people make is making the "review site" too niche.
For example, I often see people creating something hyper-specific - such as "SSD Reviews". Whilst they may gain the benefit of a direct domain name match in Google, and even industry-specific websites / magazines linking to them, they are going to be forever locked into that niche without any real way to grow.
We've found the best way to set up review websites is to make their "core" focus as broad as possible, using each "niche" as an individual category of the site. With the SSD example, this would mean you create a "computer component" reviews website, with SSD's forming part of the overall offering.
The reason for doing this is actually very important - it gives you SCOPE and DEPTH. This might mean *nothing* to the untrained eye, but at its core is a very sound principle of marketing - people *LOVE* excellence. This excellence is basically how "professional" you are at creating effective solutions to problems. And unfortunately for most - is something most people are lacking.
The bottom line is that if you create a "broad" review site (PCPriceReviews or something), what you're doing is essentially setting yourself up for being a scientific resource. You're identifying products based on statistical facts rather than just plain opinion (as is often the case with poor quality review sites). This means that if you work well on your site, you're able to basically create an effective solution that works for all sub niches within that market.
Ultimately, the key thing you need to remember is that if you're going to get involved with creating a "review" site infrastructure, you have to be certain about what you're doing. Most people have not idea about marketing and thus end up with very poor quality services that no one really benefits from.
Using the approach outlined above (focusing on MASSIVE markets), you gain the advantage of being able to adapt your offer to suit any niche you feel appropriate.