Back in July, a work-in-progress trailer for upcoming Lorax movie was uploaded to youtube, but Universal had it taken down right quick, along with any images that people had used to blog about it. I completely missed this, so I was glad to catch it when a chinese site leaked it again last month, though once again Universal had it taken down almost immediately. So it's probably in light of these leaks that the official trailer has finally been released.
Some parts are a little different from what was in the leaked trailer, and some things were left out, specifically one scene where the Once-ler accuses Ted of just doing this for a girl. And the scene at the end of this trailer with (I assume) the Once-ler's relatives wasn't in the leaked trailer at all.