If you've got a great product which a lot of people would benefit from using then getting new customers should be easy.
With the power of social media you can reach out to such a huge audience at no cost, your message will be seen and read worldwide. Do you think that alone will bring in a huge number of customers?
What about all the retweets, 'likes' and such that you're getting through your online profiles?
These alone won't bring in the customers, they're all 'activities' and every activity, taken in isolation, won't give you the results that you need.
If you implement a system, of which your social media activites play a part, then you're on the right path.
The mistake that everybody makes is that they believe the more 'likes', for example, your page(s) get on Facebook, the more customers you're going to get.
'Likes' do not equate to sales and never will.
The reach that platforms such as Facebook give you is the most important thing to gain from using social media but it's still only a part of the overall system.
Blogs and their relevance
A lot of businesses probably don't see a blog as being particularly important. It's one of many important tools in your arsenal and here's what you should be focussing on:
The content must be interesting to your contacts on social media, make it relevant and exciting.
Take your blog posts and advertise them through your social media profiles to maximise visibility.
Don't forget to include your lead magnet in the post, this will be the hook with which you'll get your contacts to opt in to your list.
Keep a regular contact with those who have opted in, marketing your product(s) to them, and they're far more likely to convert.
Social media is one of many tools to use to get people to get more people onto your list. It's not going to generate new customers by itself.