Why do people write like this here?

Yeah, this is
truely annoying..

On A Par With Typing Like This...

Or tHiS, UnFoRtUnAtElY It SeEmS CoOl If YoUr 13...

Because Most of the ones that do are 12 year old girls

so says
the talking
piece
of
gum
that
plays
pokemon.

it makes me feel dizzy

Yes, this is truly annoying.

yes I do I think its annoying.

That's a lot better than people who write like this: So AnNoYiNg.

It depends. Often on the internet on yahoo questions people dont want to read paragraphs explaining stuff, but they are very receptive to short bursts of sentences.

I don't think it's stupid. You should be more considerate. Maybe they can read better this way, or maybe they have bigger fonts on their computers and hit "enter" at the of end the line. So, most likely it's a vision related problem, and it doesn't look stupid to them.