This is something that has been bothering me about the fandom for a while, and I really hope that it can be straightened out. Let it be known I have nothing against fanon, in fact I have a fanon project on the way, and it is partly the reason that this subject means something to me, but even without this project, I would still find this a subject worth adressing.
From what I can see, the brony fandom seems to be incapable of understanding the difference between canon and fanon, or at the very least, incapable of understanding that one does not have to affect the other or obey the other, and they should both be treated seperately.
Fanon is not Canon
If there's one thing the brony fandom should be admired for, it's that they are pretty creative when they want to be. When they like a particular background pony, they create a storyline for them, and if the storyline is successful enough bits of that storyline get reused so much, that not everyone even remembers where it actually came from (Derpy being a mail pony is one example of this). They have an idea for a name to give a namless pony, and if succesful, it's the offical brony name for that pony. They have some idea about something that hasn't been shown, revealed or explained yet, so they write or draw about it, or just have it as headcanon. Then Hasbro dares to do something different, and everything goes out of hand. Of course, why shouldn't we be annoyed that Hasbro didn't pay attention to our ideas, I mean it's not like they own My Little Pony right?
Oh, hang on a sec... they actually do. You see, this is where one of the greatest quallities of the fandom turns into one of the biggest fails of the fandom. It's all very well you having your ideas, or liking other people's ideas, but they were always fanmade. Did you really think that Hasbro was going to put their own ideas aside, and go with what you said? Think about it, if you were making a show, would you get all your ideas from fanfiction? I seriously doubt it, the most your fans should expect from you is a quick refference to let them know that you care enough to check on what the fans are doing.
And Hasbro does do that; Derpy and Doctor Whooves were shown together during Hearts and Hooves Day and it has been confirmed that Lyra and Bon Bon were placed together a lot more, after it became known that bronies prefered seeing them together, not to mention that they even gave Derpy an entire scene, but to expect them to do everything as we expected/want especially if it relates to one of the main characters (though I can't think of any specific examples) come on, let's be realistic. Even with background ponies, they can't know everything that we want them to do, and not all of us care about certain things as much as others anyway.
So when somepony other than Derpy delivers the mail, or when the pony you've been calling Colgate since you joined the fandom gets released with a different name, or when Vinyl Scratch's/DJ Pon 3's eyes turn out not to be red (all of which has happened, I know) does this mean Hasbro hates us? No it just means they had their own ideas of how their own characters should be. They didn't do it to spite anyone, so stop acting like they are.
That said, the other side of the coin is even worse, I'm sorry to say.
Canon is not Fanon (or "Why Your Headcanon is Not Ruined")
Another thing that seems to happen whenever Hasbro makes up their own mind about something is that we get annoyed because our fanon (or our favorite fanon) is ruined. Except, can you please explain to me why it's ruined? Do I actually need to remind you what the first three letters of fanon, fanfiction, fanart, fanseries or fananything are? That's right, it's "fan" and do you know what that means (and yes, I know I sound like a patronising kid's show presenter here, and I'm sorry about it)? Exactly; it means "Something that was created by a fan."
So basically, now that the real show has done something differently - you can't enjoy the same fanfiction that you've always enjoyed now that it's officially non-canon? Guess what? It was always non-canon, from the moment it was created by someone who is not part of the real show, and absolutely nothing has changed about that. The same goes with your material, it is still yours, and is fanmade eitherway, and therefore shouldn't matter if a recent episode contradicted it, it was never going to be 100% part of the real show anyway (though I'll not rule out the possibility of a fanfiction/fanart guessing canon correctly) so write and draw what you want, and let others do the same. It's the fan's idea of how things should go, and each fan should be allowed to do things how they have chosen; so if you have a story planned in which Scootaloo can fly, write it. If you already had an idea of who would be a good love interest for Twilight before Flash Sentry (who exists in a seperate canon to the main show anyway) was created, keep using him or her. It's fanon, it doesn't have to obey everything the real show does.
I've seen a lot of talk that the show has been "ruining everyone's headcanon" these days. Seeing as "headcanon" is just a fancy word for "fanon" in a sense nothing could be further from the truth; again, it's up to you what you put in your work, so if it goes against the show, it shouldn't have to matter - it's not canon anyway.
Also, how exactly does Rainbow Dash's father appearing in season 3 ruin My Little Dashie anyway? Because she called her human friend "Daddy" while she was growing up? She had no memory of anything that happened in Equestria, so she wouldn't have known about her real parents anyway (sorry to mention that fanfiction, as not everyone likes it - I adored it though,)
So what's the point of all this?
The point is, that this fandom really needs to learn the difference between fanon and canon, and that we shouldn't expect canon to be adapted to fit with fan material, nor should we feel the need to change our fan material to fit everything in. My fanseries for example, is eventually going to include things I liked/that don't go against my ideas too much, but not include things that I don't like/that do go against my ideas too much. It's hard to explain without giving too much away, sadly, but ultimately it is my storyline, and is neither right nor wrong.
I am sorry for the wall of text, but I actually feel this needed to be said.