Here are my thoughts about LIN.
I am on the network for a long time, never made direct money from it but..
As LIN suppose to be a professional social network, you can use it for the following (and more):
1. Groups - there are really big groups on LIN that can be supper target to your niche - use it to grow your name/product/service and your site.
2. Magazine - There are online magazine and offline magazine in your niche, search the owner, ask to publish an article and who know where it can get you ( I did it and got nice traffic and new connection from it).
3. Product/Service - well if you have one, it can be a great place to promote it, with connections and inside target groups (as some already mention here).
4. Websites - Want a good post on a relevant niche site, search who is the owner and you can direct contact him, who know maybe you can exchange article with links....
5. Content - Ask your connection to share your content on LIN - some will do it for free, some will not.
I currently have around 4K connections, had only about 300 two month ago, I just go to my 'People you may know' and send connection requested to the list over there, I prefer to send it to people that I have more then 100 shared connection relevant to my niche or interest - I do it manually - no bot - in the morning and at night - select about 50-100 in each bulk using my mobile phone.
From time to time, I search for a company that I like or have interest in and try to connect with people in that company.
Nowadays, I use it just for connection and to share content that I like mine and others, I do NOT make money from it, but in the past been able to write to an online security magazine, promote my sites, promote a free tool that I build (fix bugs that found by people, add new features recommended by them), make connection over sea and find jobs when I needed.
Hope it help,
darklich.