I think that it just shows Wanda's not as all-powerful as she thought.  There will be an explanation eventually. 
 
Something I'd like to see is Apocalypse trying to recruit her as a Horeseman.  With three words, she did what Apocalypse had been trying to do for years - winnowed the mutant population down to a strong few.

Strange used his powers to Protect those present and maybe that messed up the rest of the spell. Also Remember Wanda had very little control of her powers then so it is likely that the spell wouldn't fully work 

I don't buy Marvel books, so no, we don't keep reading.
I refuse to be a zombie and buy shit I don't like. I haven't like more than a handful of Marvel books in the last decade.

Didn't they have some aborbing mutant get tagged with energies that have force sources in space release it all on earth again that's how magneto got his back.  The witch just got rid of mutants on earth but those who were feeding from the streams in space like antena taking radio waves or whatever were not effected by her power. As it was out of her spell range.

It's pretty clear how she messed up, she drastically reduced the number of mutants on earth.

"Why try to figure out perhaps the most case of bad writing in the last ten years of Marvel? "

I missed her.

Many of the proposed explanations sound good, but for all we know she may simply have not been able to entirely pull it off.   I don't remember Wanda being all-powerful after all.

" Did she actually mean "no more mutants at all" or just "no more mutants than there are now"? The only new mutnat birth since has been Hope after all. (Which makes no sense since any geek knows mutation kicks in at puberty :P )

I'd also like to find out what was on the other side of that door Clint opened when he met up with her.  Did we ever get an answer to that?

Is it possible that she had some sort of... whats the word..... subconscious. Thats it. Subconscious side of her that didn't want to rid the world of all mutants, so she accidentally saved some? Also, I find it amazing how even though there were only 198 mutants left in the world, most of them happened to already be in the X men. That was pretty lucky

Obviously, this act was purely editorial.  
 
Morrison put some pressure on Marvel co. by writing that in 5-6 generations, there would be no more humans. Quesada and the guys panicked and realized that since Marvel status quo has been the same for 40 years, they sure as hell couldn't change it now. So they basically "reset" the mutant progress bar putting them back in square one. X-Men's extended friend and foes cease to exist, where as just about every x-man retained their powers. Makes sense right? 198 out of billions and billions of mutants thoughout various timelines/universes, and 616 x-men retain their powers. 
 
Quality writing and highly feasible.

As far as I know the Scarlet Witch has always had some problems controling her powers.   Maybe the remaining mutants is a result of  that.   Also she was not  in her right mind at the time so that could of  contributed to that as well.

Well, perhaps Wanda's "spell" didn't instantaneously effect every mutant. The 198 could have been those that the spell hadn't gotten to before it got to Wanda. If she was depowered, perhaps that also caused her spell to fizzle out before it was completed. Or perhaps it was just sloppy writing...

" Wanda's spell was an attempt by Marvel to reduce the number of mutants because there were too many. Obviously Marvel wasn't thinking of completely eradicating mutants because we wouldn't be talking about the X-Men right now. As for an in-universe explanation, maybe someone interfered with Wanda's spell. Someone like the Phoenix Force. Because if you think of it, Hope was born almost immediately after the Decimation and we all know that Hope has a connection with the Phoenix Force. "

I think she messed up on a lot of things. She didn't bring back Vision, nor Magda or Anya. I don't think Magneto would have tried to get Wanda to change reality  back if he saw his dead wife and daughter. She is not God, but just a mad confused and depresed woman who needs help in many ways. I don't think she ment to realy hurt anyone, she was kind of doing the "I hate you dad, I wish you were dead" thing. Isn't her powers basied on probability as well? That also could be a reason why not everyone was depowered.

she forgot to add the word " ever " at the end.
she was tired, she had a long alternate reality just then.

Wanda said no more and the Phoenix said hell no

Think for joining. Even if it was only to Marvel bash. Could you please justify DC's constant continuity reboots for me?  Thanks :D XXX "

" i thought that Dr. Strange and Emma Frost cast an astral shield and could only protect so many mutants... "

marvel isn't crazy to throw away the x-men titles lol

Meh, grammar nazi! :P

Still too many mutants.

It was a mutant culling. The whole House of M was a joke - and even now, I still don't get it.

marvel isn't crazy to throw away the x-men titles lol

It was a mutant culling. The whole House of M was a joke - and even now, I still don't get it.

Scarlet Witch too hipster, she wanted most of the mutants to go away

The powers that be needed a way to reverse everything Grant Morrison had done (i.e. the extinction gene, exploding numbers of mutants, mutant culture, etc.), and Scarlet Witch provided the most easy way to do it.

@moywar700 said:

Yep, the mutant population was beginning to become a sizeable population which took away their minority angst, an the powers that be desperately wanted to hit the reset button since most writers have no idea what the X-Men's relevance is witout this story angle. I was very annoyed that the "Children's Crusade" had so many characters acting WIS/PIS. Scarlet Witch could have, for example, tweaked her spell so that only mutants who liked their powers would get them back. Instead they had Patriot act out of character, made Dr. Doom look stupid and had a bunch of heroes standing around gawking.

Well Hello everyone, I came here to answer the puzzling question about why not all has begone by her evocation. The reason why is because she said "No more mutants" but she did not evoke the words "No more Mutates" which would be the end of mankind if she did evoke on mutates because mutates are not born Earth x mutants, they are just normal humans that got caught up in some bio goo granting them powers instead of life threatening cancer but even normal humans...the entire planet have some type of genetic mutated cells like tumors, cancer, ringworm's, chicken pops etc and so she would have destroyed us all.