If you're playing the downloaded video locally, the ID is not necessary. There are some video library tools that can use the ID to pull video information though (actors, description, etc).
As for funscripts: local playback only requires the video and script to be named the same--you can name them whatever you want, they just have to match. If there is an application that can automatically pull a funscript from some random database somewhere to match a video downloaded from SLR and played locally, sign me up and take my money.
