SEO is about so much more than just keywords and title tags nowadays...Now, ever more than before - links are just as (if not more) important...Sure, you could still rank for some keywords purely with good on-page SEO, but to truly have an overall strategy you will need to implement some form of link building if you want to make some large significant gains on your traffic.And especially if you have an online business/ecommerce store, this is essential.