Is it true that you get banned straight away from search engines if you use blackhat SEO techniques?
I assume not, because i see ALOT of sites using it

Well they dont catch everyone, like you said.
But you can always report to google if you see sites using illegal methods.

Eg, BMW recently got banned for doing this, so its certainly not impossible.

Ok, so alot of people get away with it.
That sucks...

Not that Im going to try it, I just find it interesting (and annoying)

I remember that.
They said they didnt know it was happening, that they just hired an SEO "expert" to do it all for them.
Some expert!