Should your blog be on the same root domain and design as your marketing site?
As an example, here are some companies that DON’T do that (blog on different subdomain or domain from their marketing site and completely different design), and they seem to be doing just fine. 
Curious about the pros/cons are of either approach.
This is an interesting question. I never have really thought about it, but have just spent the past 10 minutes looking at those blogs and thinking about why they might have done that.
My guess is that it might have to do with technical reasons, if your marketing site is simply a couple of static pages built into your app, a dedicated URL for a blogging platform would be a simple solution. As far as design goes, these popular blogs above have layouts optimized for blog content, instead of fitting a blog into their marketing site layout. Probably a wise decision.
People in the SEO field generally claim that you get better SEO results for http://example.com/blog than you do for http://blog.example.com
However if you use a third party blogging platform like blogger.com then it is easier technically, perhaps to use a separate sub-domain.
Ultimately, either approach is fine.
There’s a common technical reason for having your blog on a subdomain.
If you want your blog to be part of your domain, but you don’t want to host or manage the blogging platform yourself, third-party blogging platforms like Tumblr will allow you to set up blog.yourdomain.com with a simple one-line change to your DNS settings.
You get good tools, with nice themes, on your own subdomain, with 2 minutes of work.
We do this for Uberdeck.
I understand the technical reasons people do it…I’m saying let’s assume there aren’t technical limitations. Should/shouldn’t you do it and why/why not.
I always kinda wondered why some of those companies choose to go with the subdomain. Why miss out on the SEO benefits of having all your content on the main domain?
I suppose the idea is to create a truly unique and different property. blog.company.com is an educational resource, with it’s own visual style and content. company.com is strictly a marketing site for a product.
Still, I think you can differentiate the look and feel of the /blog/ section of a site.
Matt cuts says in this video https://www.youtube.com/watch?v=_MswMYk05tk that it NOW DOESNT matter if you place a blog on a subdomain or subdirectory in terms of seo.
He says whichever route is easier for you to install is fine.
Being a heroku user this is a great relief as placing blogs in a subdirectory was impossible (i believe) if you wanted to use something like wordpress for the blog but rails for you heroku hosted app.
Hope that helps.
In general, I prefer the subdirectory approach, but it’s nice to know that it doesn’t make as much of a difference as it used to.
Anecdotally, I’ve had stuff get a lot of links on both a subdomain and a page on a root domain of different sites, and getting links to content on my root domain tended to have a bigger impact on my other pages ranking than getting links to a subdomain.
I just heard an interesting note about the SEO aspect of this…
Apparently Google tends to show only one domain per search results page. So having your blog on a separate domain or subdomain could help you show up more than once per page.
Interesting SEO benefit of separating the two.