i think voiceover (VO) in trailers is a thing of the past.
i could be alone in this, but doesn't it get old hearing the same script for trailer after trailer? that's because VO is corny, old-fashioned, and it invariably always follows the same structure: "Amy Green was just an ordinary advertising executive. But one day, she fell into a sea of toxic waste and came out extraordinary. Now, she's about to discover..." well, you get the idea.
in my experience, VO acts like a crutch: if you need it in a trailer for the story to make sense, that probably means the trailer's structure doesn't stand on its own. and even if that's a failing of the film (as in, the plot falls apart, the concept is too complicated, the movie makes no sense)--it doesn't matter. it's the trailer-maker's job to create a story.
personally, i prefer no copy at all. no VO, no cards. nada. just let the music carry the spot, with a few choice dialogue lines. however, i do enjoy a good card run when the writing is clever and/or moving and/or works particularly well within the trailer. unfortunately, that doesn't happen often, so most of the time cards wind up being uninspired and clichéd.
the only text i like to include in trailers are reviews and festival laurels. i think those speak louder (and say more about the movie) than a trite play on words.
for example, check out the awesome trailer for the film JCVD. look at the way they use reviews in place of any copy/VO. the reviews elevate the film while still complementing the trailer's tone and structure, and they even assist the act transitions. (also, just because you're already watching it, stick around until the end of the piece--the final picture montage is incredibly well cut and one of my favorite things to watch.)
now compare the JCVD trailer to something like the trailer for the upcoming film Drive Angry. here you have the same tired VO set-up (see above for my example and look at how well this fits), followed by a super clichéd card run. (sidenote: how many times does “hell” come up in this trailer? SIX.)
it looks like they had enough footage to create a fun trailer, but instead of making it original and interesting, they went with what we’ve seen 100 times before.
the last word on VO: there is a special case when VO works well in a trailer, and that's when it's lifted from the film itself. if a movie has a narrator, and the trailer incorporates the narration into its structure, that usually results in a unique spot. that's bc the tone/feel of the movie will translate into the trailer--and the VO itself will be more specific to the film. check out the (500) Days of Summer trailer (which is awesome) for an example.
final note: please keep in mind that when i critique a trailer, it has zero bearing on the film. i’m solely commenting on marketing materials.