One of the most prominent use cases for LinkedIn is an email from a recruiter who is pursuing you as a potential candidate for a role they are sourcing. Here’s an example: 

In the event you respond that you are not interested in the role, recruiters will often follow up and ask you if you know anyone in your network who would be a good fit for the role. Here’s an opportunity for LinkedIn to automate this functionality by having a separate CTA that lets you refer someone in your own network. Consider the following draft mock: 

By clicking through, the user would have the ability to specify one or more connections in his/her own network to be referred to the recruiter. On the other end of the transaction, the recruiter will receive a LinkedIn message including the profiles of the referred candidates. A classic win-win-win situation.