You'll have pros and cons if you decide to go ahead and deny the unregistered to your content as it may actually hurt traffic initially, but encourage repeat users to continue visiting.
In the end the website and what it offers is what will determine if users continute to visit or not - If you just continue to offer content as well as try to improve your SEO (by including blogs or other articles that are regularly updated, which is very good for SEO) you will just get a larger bulk of users, and statistically some of those users will give you feedback and your exposure will grow.