I caught it off my f-list (which naturally was a YouTube vid) as I haven't been to a movie in ages. In fact, I'm not even sure what was the last movie I did watch...? *thinks about it and draws a blank* Maybe X-Men 3? I'm not sure...
In the trailer, it looks as if Dumbledore's Army isn't being created solely because Umbridge turns the DADA into a text-based subject (aka what the book has written) but more that Harry wants to fight Voldemort and if Voldemort has an army, Harry needs one too. At least, that's how it is clipped to be -- not showing Harry debating/deciding/thinking about teaching his friends Defense because Hermione suggested it (and because it is the year their OWLs are coming).
Like Rita Skeeter's role was slashed and made into this teeny tiny inconsequential part in GoF (I mean, honestly... if she wasn't going to cause trouble between Ron and Hermione - aka making Hermione seem like she's Harry's girlfriend and causing Mrs. Weasley to turn cold to her; nor was her animagus form going to be discovered, and that Draco collaborated with her; and the actress was not reprising her role in OoTP, it makes it seem like the whole 'tabloid newspaper'/gossip reporter part will be dropped in OoTP), then it seems like Dolores Umbridge's role will also be slashed and though she may be vicious in the parts they decided to keep, she won't be the woman everyone loves to hate and her reign of terror may be lessened.
Which then makes it seem like the whole Snitch plot might fall apart? If Harry creates the DA to fight Voldemort (instead of like the book - where they just practice defense for their OWLs), then he would recruit people he knew and/or trusted. Again, there is no cast listing for Marietta (unless she is just a minor/cameo which is 'uncredited') which makes me wonder -- and cringe -- if they will be forcing Cho's character to become the snitch (I HOPE NOT!) or simply dropping the Snitch plot (or maybe giving it to their newly created character, Nigel? -- who the heck is Nigel??? Is he supposed to be Colin and Dennis Creevey combined? [since both Creevey brothers are MIA as well]).
Speaking of new characters *grumble/sigh*, I am amused by the description off Yahoo!Movies for the DA picture. Two boys are credited as: "Slightly Creepy Boy" and "Somewhat Doubtful Boy", though in Veritaserum "Somewhat Doubtful Boy" is Zacharias Smith. So who's "Slightly Creepy Boy"? I think Ravenclaw by color of tie, but since when did House colors determine a character in the movie (e.g. Padma Patil)? Maybe it will be "Slightly Creepy Boy" who will turn snitch. After all, his name implies he's uh... slightly creepy?