Teaser Trailer Analysis - DISTRICT 9

This is the main theatrical trailer for District 9, it moves further away from the enigmatic nature of teaser trailer's as shown in my other two examples.
This trailer says a lot more to the audience about what they will get when they watch the film, good CGI effects, an interesting plot and good characters.
There is information on the backstory for the film told on the text boards which fade in and out at several points throughout the trailer. They read:

-THEY CAME HERE 28 YEARS AGO
-COEXISTENCE HAS NEVER BEEN EASY
-WHY WON'T WE LET THEM LEAVE?

-PETER JACKSON presents a film by NEILL BLOMKAMP
-DISTRICT 9
-AUGUST 14
-DISTRICT9MOVIE.COM

I'll use this in my own trailer so the plot has slightly more clarity. These text boards must sound gripping and explain the backstory as much as possible in as few words as possible.