**As a general rule of thumb, I’m fairly conservative about adding media.**

I feel like media draws attention more than text (look at teh shiny), so I don’t want to add it unless it adds clear and indisputable value to the post. Usually this means my media edits are fairly minor.

Two examples spring to mind:

1. **If the OP clearly knows about the media, but hasn’t found/inserted the item in question.**

  For example, if the OP makes reference to a video clip, but can’t find a link themselves. Adding a YouTube link/embed to the video in question would be fine.

2. **Improving the quality of existing media.**

  For example, replacing screen grabs from a back-of-the-cinema video with one from the DVD release.

In both cases, the change to the post is fairly minor, and I don’t think the OP could have much objection to the edit.

Otherwise, if it’s anything more substantial, then I usually leave it as a link in the comments. The OP can see it and add it if they wish, and other readers can find it, but it doesn’t change the original answer.