How helpful is Tumblr in seo marketing and business ?

What is Tumblr?
Tumblr is a microblogging platform and social networking website founded by David Karp and owned by Yahoo! Inc. The service allows users to post multimedia and other content to a short-form blog
There are 130.5 million blogs on Tumblr, as of August 2013
28th highest traffic site on the web according to Comscore
300 million unique monthly visitors according to Yahoo
Why Tumblr has a huge potential for SEO and social media marketing ?
With a large number of users Tumblr is good for business
1) Use a Custom Domain Name
You can have a customised domain name for your Tumblr blog which means you can use it as a fairly limited functioning website or as a primary blog for your business.

2) Dofollow links
When you consider the social aspect of Tumblr. Tumblr has social sharing functionality called "reblogging" in which Tumblr offers you a Dofollow backlink for each link you share.If you have a popular post it will be reposted to many other tumblrogs with backlinks. That means if you have a post that is reblogged 10 times, your tumblr blog just got 10 dofollow backlinks! you can also include link within the post itself. By doing so, both your original post on Tumblr, and the site linked to within the post will receive the backlinks.

3) Tumblr tags
Tumblr has a features of tagging which is very useful. If you want to add a tag, simply start typing a word and Tumblr will suggest you the relevant tags. Tumblr tags are already used for content discovery. Thus by using relevant tags, there is a good chance of your content to be discovered.

4)Optimised for Mobile If your existing website isn’t easy for mobile users to use or navigate and you don’t yet have the time or the resources to spend optimising it for mobile, a Tumblr blog will help to give you a mobile presence. Your website designer can tell you more about this.

5) Interlink with Google Analytics
You can monitor and analyse your traffic to your Tumblr blog using Google Analytics.

6) Photos
Photos section is very popular in teenagers so use a clever caption and get more backlinks.

7) Branding
Tumblr is an excellent platform for promoting your brands. With Tumblr becoming more and more popular, it’s a perfect marketing tool for businesses that are trying to extend their reach. With more than 300 million unique users, you can easily promote your brand. By posting quality content, you will have a strong online presence on Tumblr.