It's funy : you say you don't agree with me
but your whole post is to explain that some
people want to express some opinions but without
anybody knowing that it is their opinions...

That's exactly what I said : they don't want to
endorse their own opinions. They don't want
that other people know it's them who wrote
something.

Sure, on-line, we know people only by what
they post/write. So what ? The person may be
very nice when you meet him/her or totaly
insufferable... does that change anything
to the validity of what they write ? No.
Does that change anything to their argument ? No.

On the other end, I think it tell a lot about
someone when he/she posts anonymously to
criticize other people.

By posting anonymously, especialy when it's
to say something about someone else, you prevent
the other person to answer you. That's coward.

It also remove any credibility to your claims :
why should anybody believe someone who claim
to know a subject when it's not possible to
check that person credentials ?

For example, if I post anonymously to say that
this or that cel is fake, nobody can check if
I have any knowledge or reason that let me put
such a claim. Also, I prevent the owner of the
cel to answer me and I don't take any
responsability for my action.
On the other hand, if I post under my own name,
people can check if I have any reasons that
allow me to make such a claim. And I will
have to bear with the consequences of what I
wrote.

Most people doesn't post anonymously to express
less-than-popular view as you said. They post
to criticize or accuse other people. They post
to deceive and manipulate other people.

You get dealers that post anonymously to say
how great they are (real). You get people
accusing / flaming other people not on real
matters but because of personal grudge. (quite
often)
You got people posting pro/con an idee but
hidding the fact that they may have some selfish
interests that have nothing to do with their
pseudo-arguments.

In all those case, if the readers had more
information about the poster, they would have
had a wholy different interpretation.

Let's take as example those recent post about
deputy services to bid on Yahoo Japon.
I am ready to bet (an advice : don't take that
bet... I am cheating) that quite a few of the
anonymous posts against those services are from
dealers. That make me wonder if the reasons
they write are realy valids or if it's just 
excuses. Maybe they just don't want to have
more competitors or lose their monopoly
on this source of cels... Perhaps it's true.
Perhaps it isn't. One thing is sure : by posting
anonymously they are hiding part of the facts
and try to manipulate people.

What about someone saying bad things about a
dealer anonymously. Maybe if you learn that
the poster in another dealer, you may consider
things differently : perhaps the person posted
to try to hurt another competitor.

What about a seller posting bad things about
a so-called customer because he has a personal
grudge against him ? The so-called customer may
never even had ordered from that dealer...