i know that it's means it is or it has, while its is a possessive pronoun (my, your, his, her, its, our, their).

But I'm still seeing its written as it's even by native speakers all around the internet (I know, internet is usually not a good example of a grammatically correct language, but...). I would understand it more if people were just too lazy to type the apostrophe and would misplace it's with its, but the other way around?

So, my question - is it somehow correct?
Is it possible to correctly say for example "The cheetah is known for it's speed"?
And - how "bad" this mistake is, if it really is a mistake?
Just out of curiosity, I won't use it myself.

(In fact, it does give some sense, it follows the pattern Michael - Michael's; student - student's; it - it's.)