I've been recording podcasts and screen casts for a while now. I've always ran all my audio through Audacity and used the noise cancellation to clean up the audio. I've been happy with the results generally.
I was attending a conference session on recording videos and they suggested recording some silent room noise, and then mixing it in the entire recording so the background noise was consistent after editing. I asked him why he didn't just remove all the noise instead. He said that the background noise sounded more natural, and noise removal distorted the audio too much.
I know that not dealing with the slight amounts of background noise is not a good solution for edited audio since the change from noise to no noise, or different noise is very noticeable.
I don't have any training in audio production, so I am curious what is the recommended method of dealing with this. Is adding bed noise the preferred method? Does using active noise cancellation really distort the audio that much (and I just don't notice it)?