Video annotation for object tracking completely changes the game. Now, an entire video sequence can be assessed as a whole, whether the clip contains 2 frames or 2,000 frames. This feature makes it much easier and faster to follow a single object -- even if it's moving -- from beginning to end of a video. If the object disappears from the camera view and reenters later (think: overtaking a cyclist in traffic, only to have them blow past you at the next intersection), we can easily, accurately accommodate it. The whole process is more efficient while maintaining the highest annotation quality, especially as the density of objects increases. And believe me, image complexity at the cutting edge of computer vision is getting up there.