Check out this thread:
http://www.letsrun.com/forum/flat_read.php?thread=4660650
Seems awfully familiar...
GG (then GA) was DQd for contact Amy Mortimer, but then reinstated on appeal. You'll also note that there are allegations from Morgan Uceny about GG pushing her in the prelims.
Then there is also this video near the 2:20 and then 2:30 mark:
Lots of jostling and shoving going on around/because of GG there.
This evidence begins to paint a picture of GG as an aggresive/pushy racer. Maybe none of these events warrants a DQ, and maybe GG's actions in the 3000m did not warrant a dqDQ but when you make a habit of this kind of conduct its not surprising that it might result in a DQ at an unfortunate time.