I am not sure where these myths come from, but someone asked Google’s John Mueller in Friday’s Google Hangout on Google+ at the 11:15 minute mark if it is something Google may penalize for if the site doesn’t link out to other sites. The person said they heard Google issues penalties when site’s don’t link to other external sites.

John Muller from Google quickly said there is no such penalty.

The question asked was:

John responded:

John also told us there is no SEO benefit to link out, which was refuted by an SEO study later. There is definitely a fear of linking out which is sad.

John added his personal thoughts saying:

Which echoed what Gary Illyes said in a more “PC” way, where Gary said it’s stupid not to link out and it makes him angry.

Here is the video embed:

Forum discussion at Google+.