Would a private blog network be effective for SEO?
 

I understand that today link exchanges are amateur and are not as effective for SEO as they were a few years ago.

Let's say I build a private blog network of 10 - 20 sites, all with unique content. Let's also say I use about 5-6 different themes across the sites (so some sites will have the same theme).

Let's also say I use private registration and I use a different cloud server (with different IP addresses) per site for hosting.

How effective would a private blog network be for SEO?

I think if you do them "correctly" they will work

I am not sure. But as you noticed already link exchange is not so effective nowadays. I read a few days ago that Google is going to integrate new algorithm where reference weight will not included and will not give pluses for SEO. One of the main property which Google is going to estimate, it's user's queries and your content. The more your content is matched with users queries, the more weight your site has. I'm not sure that this is true, but I read it on the Internet :)

if the domain have authority it would work

Blogging is less popular than tubes and sometimes it's difficult to promote own tube, I think you understand me :winkwink:

Check in Your Google Webmaster Tool If they are Good for your website.In my opinion it is the right Thing to do.

I generate webmaster traffic using this theory.

Yes, this is an effective method.
Make sure to do your homework on how to properly build a PBN and you should be good.