Now, Firecracker, yes, anyone can indeed review any new product on a blog, and there are unlikely to be any issues with trademarks unless they are 'passing off' or otherwise trying to get some sort of financial advantage from the use of the trademark, as distinct from the review itself. And they can say whatever they like as long as it is not libellous.
The thing is, how much are most of these reviews worth? Often, they'll have spent their own money to buy the kit in question (and therefore need to persuade themselves of the value of their purchase)
and they will have very little knowledge of the competition.
This is where a 'hard copy' reputation comes in handy. First, you can borrow stuff from the manufacturers, interview people there, and so forth (hence my three upcoming factory visits this month, Leica, Zeiss and Manfrotto/Gitzo). Second, you get to handle a lot of kit, allowing a basis for comparison. Third, your readers have some idea of what to expect: they learn your biases, your style, your strengths and weaknesses.
The reason I've put so much work into
www.rogerandfrances.com (including reviews -- I'm working on the Leica M8 at the moment, which I've had 6 months) is that I'm much more interested in (a) how to take pictures and (b) silver halide than in the latest digi SLR and software, and this is not the direction that book or magazine publishers are taking. In fact, a week or two ago I put up a huge new wodge of free modules called 'Basics', largely in response to something I read here on APUG about the dearth of well-informed but really basic information about 'real' cameras.
Incidentally the M8 is gorgeous, the first digicam under $20,000 I've really wanted as a general-application camera, not just for the convenience of product shots and special applications such as soft focus (Lensbabies and Dreamagons are wonderful on the Nikon D70). But I think the next review/report will be the Alpa.
Returning to your question, what has hurt magazines most is not 'camera porn' but e-bay and manufacturers'/dealers' web sites. Look at the classifieds and other ads in a Shutterbug from 10-20 years ago and you'll see what I mean. Ads are what pay for most magazines: cover prices would be several times higher without them. Increasingly, the main reason to advertise in magazines is to show your commitment to the medium -- which is also why people sponsor this site!
Cheers,
R.