Here are some reasons why people may use LinkedIn.

- To stay in touch with friends and colleagues. 
- To reconnect with old friends and colleagues that you may have not been able to find or be found by otherwise when emails and phone numbers are changed. 
- To get introduced to new interesting friends and business connections. 
- To promote your products and services, find or be found by new customers. 
- To find or be found by new vendors, suppliers or service providers. 
- To find a job through your network and to make it easy for employers and recruiters to find you. 
- To find someone to fill a vacancy that you may have. 
- To find experts and get advice. 
- To share your experience, help others and give advices. 
- To stay updated with the latest news especially about your network and what’s new. 
- To join groups and start or join in interesting discussions. 
- To build and strengthen your personal branding and online presence for you or your company (improving the chances of being found on Google). 
- To find new opportunities for business, partners or investors 
- To consolidate in one place trusted (to some degree) recommendations that you can get from your colleagues, friends and business contacts. 
- To use who you know in common to ask for reference about someone or a company before working or doing business with them. 
- To look up anyone that you need to meet or speak to and find out what you can about them to understand them better and to make a good impression. 
- To be able to post questions and get different answers 
- To be able to create or participate in polls (surveys) and find out the results. 
- To be able to post and share announcements, updates, news, cool things. 
- To be recognized as a subject matter expert in your area of expertise. 

As you can see the possibilities and power of this network are endless.