One classic trademark of comic book fans awaiting for a much desired movie adaptation of a beloved character is impatience. "Okay, that was the teaser, when is the next trailer out?!", "I wanna see some footage!", "the TV spot didn´t have enough new footage!", and so forth. Which is part of the reason why studios don´t release only one trailer, but usually one shorter teaser and then two longer trailers, not counting international trailers, TV spots, etc., to let non-fan audiences know about it and get interested, but also to whet the fans appeti´tes and get the feeling of what the early reaction is.
Another classic trademark of said fans is, they can be very picky with the material they receive, sometimes for good reasons, sometimes for bad. One common complaint associated with early teasers and trailers is the FX. Those in the know are aware that a movie´s post-production, particularly for a big-budget summer popcorn blockbuster, is a long, extenuating process that takes several months to get done. Material that´s released several months before the movie is very likely to not be 100% done, and when it comes to FX, especially, the devil is in the details. Some will remember a Super Bowl spot for the first Iron Man, that had a final moment of him fighting a tank. The background looked almost Playstation 1 bad, but then the movie was released and the scene looked a lot better and more realistic. Or, more recently, Thor footage leaked on the internet, and some fans were worried that the FX didn´t look great and that the movie was going to be too set on Earth and "cheap". Now the trailers show the same sets from the footage in much better detail, and we´re getting lots of asgardian coolness.
When the first trailer for Green Lantern was released, last year, there were two main outcries. One was for what was considered excess of comic relief, but that can be at least partially blamed on Entertainment Tonight. They cut a 30-second tease of the trailer, highlighting its sillier comedic moments. The other, however, was the CGI, perceived as subpar. Now, not only GL is a highly demanding production in that area by definition, with alien planets, lots of alien GLs, the power ring constructs, etc., but they decided to make even the suits CG, as to highlight them as an alien technology created by the ring, instead of a regular fabric suit, which is how it´s explained in current comics anyway. It´s one of those situations, like a human being moving like a spider, or a giant green square-shaped humanoid monster, where you can use the best FX in the world, but some part of your brain still will tell you that what you see isn´t real, for the simple fact it´s something that´s not possible or has no reference in the real world. Now, we wait and wait and wait, it´s March and no new GL footage has been released.
Then there´s Captain America: The First Avenger. There were lotsa rumors of the first teaser being delayed cuz footage "wasn´t amazing", then director Joe Johnston himself rectified that they were trying to get the FX as finished as possible. The first released footage was the Super Bowl spot, and it was actually quite well-received. But then again it emphasized story, focusing more on the transformation of Steve Rogers and his character than in big, spectacular action scenes filled with FX. Now we keep hearing about a second trailer, even saw a supposed description of it online, but no date seems settled for it to be released, and again we get rumors of delays.
All this put together, it´s not crazy, I think, to speculate that studios could be getting scared to release trailers and are further and further postponing them so they don´t get mixed reactions like the GL trailer received. On one hand, fans will enjoy to see more finished products that look more like what the final product on screen will be like, and avoid pulling their hair in fear for nothing - another very common trace of fanboy behavior. On the other hand, studios need to put effort to make the audience aware and excited for their movies, and the reverse effect of that is now we get a lot of fanss worried that the studios aren´t marketing the movies that much and generating enough early hype for them to do as well at the box office as they potentially can. We may have to learn to be more tolerant of early material, or more patient for the better product. Sadly, both tolerance and patience are somewhat scarce in the comic book fan community.