I have a website that contain all user generated content. The users are free to add links to the content. I also provide my users with an about the author column, where they can add links too. All the links in my site are dofollow, as of now. Is this an SEO threat? There is a strong editor system and people are not allowed to spam, but there are more and more articles and about the author columns coming up with outgoing links.Nofollowing all external links is an SEO threat, as some users say. 
Too many outgoing links due to user generated content - is this bad for SEO?
seo;links;dofollow
As long as the number is balanced and the link targets are not spammy sites, then there is no reason to worry about.However, you may want to add some sort of filter that allows dofollow links only to users with a trusted reputation.Another alternative is to limit the maximum number of links in a document. You can either set an absolute limit or compute the limit in percentage depending on the article length to make sure the final result is more natural.