In theory, it's a good idea. But like the other posters have mentioned, it's an uphill battle. In my experience (Application Developer), creating the content management side is easy. Creating the content and building a subscriber/user, that's an entirely separate -- and exponentially more difficult -- endeavor.
* How would you entice professional photographers to review equipment on your site? To start, I imagine this site would have low traffic and small user base, so for a professional photographer to take time away from their job, you'd likely have to pay them.
* How would you manage the content? Would it be a free for all, or would you have an administrator?
* What would be your source of revenue? Ads are great, but given the saturation of market (I mean, you're posting this idea through a competitor) I can't imagine you would recoup your investment (time, capital, etc) very quickly.
Frankly, this idea kind of sounds like facebook for photographers. Which, again, isn't a bad idea... but having built these sorts of tools in the past, I can guarantee getting it off the ground would be more challenging than you think.