Leosghost - 7:34 pm on Jun 4, 2011 (gmt 0)
A site may touch more than one niche, but if the signals are clear and unambiguous as to which niche is it's primary focus, the search engines will pick that up.
If it is trying to be too "catch all" ..it will be weak in all ..and thus weak overall..in all the niches it touches.
Breaking up sites into smaller sites or at least into very distinctly focused sections will help search engines to decide the "niche" you are trying to compete in better.
Amazon has reviews, but it is definitely "selling" ..the best camera review sites are definitely "review" sites, feeding it and other sellers ..some review only or mainly "DSLR" cameras ..some only or mainly "compacts" ..make it obvious what "your niche" is , and you'll rise above less focused sites.