This whole story aggravates me. I tried to watch this "video proof," but I'm not sure I know that the video has been edited. I was looking for that jump cut or obvious cross fade...but I didn't see it. I suppose I now know why it was so easy for media outlets to believe it, but that's the thing- if it's easy to believe, or "too good to be true," it probably isn't. However, it was true that Sherrod said everything she said, Breitbart just selectively edited Sherrod's speech and showed us something taken extremelt out of context.
The way the story spun out of control reminds me of when Joe Paterno's death was reported too early. He died, then he wasn't dead (just kidding!), and then he later died. The media spun out of control, reporting the wrong facts, tweeting them out, deleting and later apologizing.
What this should teach us as journalists is that fact-checking and sourcing is of the upmost importance. If there is no source for the information you're getting, you can't be quick to believe it. If there's no source to back the source you're getting the information from, you still can't believe it. Don't just run something to get good ratings or get the story first, run it because you know it's factually sound and ready for the public to consume.