Youtube is a website that allows you to upload and host videos for the whole world to see. Youtube plays an important in DYOM and it's advertising.
DYOM Video Reviews with Commentary
DYOM Video Reviews with Commentary is a topic created by Doublepulse. It is just like a walkthrough, but has commentary. Youtube is a great place for uploading the videos. Not only do the DYOMer's see it, someone browsing through videos for GTA SA Mods might see a DYOM video.
Tutorials and Trailer
Again, Youtube is a great for DYOM videos. Things like tutorials and trailers can be uploaded. Take a look at Dutchy3010's channel.