Inbound link, also known as back link or in link, is a link from a domain other than yours to your content page. The importance of inbound link is well known. And reward inbound link, as Rohit put it, is the Rule No.3 of SMO, or Social Media Optimization.
Some would think of this rule as a more SEO than SMO. To some extent I would agree as this is really important for SEO.
However, the difference here is, in this Rule, people Choose to link to you rather than requested. They are more engaged. This may be because you are famous, but often times because you have produced excellent contents, be it articles, pictures, videos, etc.
So, why on earth is inbound link important for SMO that we should reward it?
We understand the importance of inbound link to SEO: it is for the love of search engines and hence the traffic from them. Same is true for SMO. Media is the means of communication, which is right the higher application of Link.
In SEO we need links, while in SMO we need communications. In SEO we beg and pay for links, hence in SMO we reward communications
Now, the question that remains is, how to reward inbound links.
While there are a lot of things you could do, I would like to suggest the followings:
1. Put trackback links to those who link to you below your contents.
2. Put favorite links(or whatever you may call) to their sites/blogs.
3. Mention their names or sites/blogs in your contents.
4. If necessary, write a review on their sites/blogs.
5. Send small gifts to them, be it digital or real.
You don't want to do anything further as it would seem that you are too eager to get linked. Be decent and don't let any of your thanks seem like Ads.
And you may probably argue by saying "I'm able to reward all that link to me!". Well no one is.
Then what do we do? We give rewards to those who are most active and relevant ones and that would be enough. Because you have rewarded, that would be good demonstration of what you would do when people link to you. And you've set up good examples for people to follow.
But don't worry too much about how and who you will reward. Because that is not the important thing. The important thing is, keep producing outstanding contents for people to link to you.