Markus,
We shouldn't. The reality is that the immediacy of the fora
almost asserts itself. If you say something completely mad,
someone will come and contradict it. This will balance the
opinions out. Noone is necessarily right or wrong, but there
is an open exposition of opinions. Everyone is free to make
their own judgements and draw their own conclusions.
Moreover, generally people that write in these fora are not
called experts by themselves, instead sometimes being
recognised as such by others, for their merits. That, to my
mind, is a much fairer way of qualifying opinions and asserting
expertise.
One last remark: i buy mags, and not just because of the
smell of the paper.

At best, they tell me what gear is
coming out, what their strengths and weaknesses are,
and how they work with one or two types of equipment.
It is however very difficult to find in a mag all the combinations
of equipment pairing that one might want to find out about.
If I want to know how well (or not) a certain speaker will
work with an amp, or a source, the chances that someone
in a forum has tried that combination and can give me some
guidelines is much higher. It is no conclusion but it can
help a lot. And save people from going blind into bad
combinations.
Each to its own. Mags are useful and i respect a lot of what
is written there. Same goes to the fora. In the end we all
follow our ears, or so we should.
Jack