Mapping Center Answer:

Unfortunately we don't support either labeling or annotation features directly in ArcScene. Interactive placement of text graphics is one of your choices for incorporating text inside the 3D view – see the attached screenshot. The other option is to post-edit the exported video file and add on-screen text (e.g., using Camtasia).

Information on how to put 3D text into the ArcScene view is available on this online help page: "Digitizing a 3D text graphic in ArcScene". 3D Graphics Text and digitized text is hooked to a geographic feature/object in the scene. Use the graphics layer to create a layer animation, which would turn on/off a layer containing graphic text. So, when you move around in the scene using a camera animation, the graphic layer is turned off/on when desired. Alternatively, you could create a custom animation type (programmatically) which allows for showing text at different times during the time animation. Unfortunately both are a bit hard to achieve at this point.