Although building a subscriber base does not need a blog or a website it can help immensely. An opt in form on a blog will not convert nearly as well as a standalone squeeze page, and this is because there is a lot of distraction on a blog. Remember the landing page or squeeze page has only one purpose to make the viewer opt in. On a blog, there will be lots more information to read and possibly other ads to click on and so conversion rates dropped dramatically. However, the blog does have a useful purpose in that it acts as a hub where people can see that you are a real person. It backs up the connection and of course the blog post can be much bigger and contain more information than an email ever could. In fact, the more social platforms you link to, the more the blog becomes the center hub and the email marketing feeds off all of this.
Although as we said the conversion rate is lower on an opt in form on a blog it still makes sense to have one on the site as it will still bring in a steady trickle of new subscribers. So not vitally important and on its own as it would be a poor way of creating a list, it still makes sense though to have that in your arsenal.