NoFollow tag for external links: Good or bad?

[WebServiceConsulting.com]

I have a few sites that have tens of thousands of links on them (most of them are sourcing images that happen to be external links).

I know that it's a good thing to externally link to reputable sources, but is it smart to place the nofollow tag on ALL external links? I'm sure there is a good chance that external links from posts from years ago are pointing to sites that may now be penalized. I feel as though nofollowing all the external links could come off as unnatural.

What are the pros and cons of placing the nofollow tag on ALL external links, and also if I leave it as is and don't put the nofollow tag on them.

Thanks.

[Chris.Menke]

102,

No harm is going to come to your site if you nofollow all of those.  If there's some likelihood that a good many of those links are pointing to sites that are penalized and I had to do all or nothing, I'd nofollow all of them.

[webmethod]

I don't think nofollowing lots of links would be unnatural, as it doesn't strike me as a quick "hack" to boost your rankings. If nofollow was taken off lots of links then that might be something Google would pay attention to as PageRank would then be passed to these links.

If you can't endorse / trust the links then nofollowing them is what Google recommends:

https://support.google.com/webmasters/answer/96569?hl=en&ref_topic=2371375

If you want to be extremely cautious then you could add nofollow to the links on some of the websites, and see if anything bad happens before doing the rest.

George