Informational interviewing is key to expanding your existing network. You don’t need to take someone out to lunch or spend two hours in a coffee shop with small talk in order to build a connection. You can gain a contact in as little as 10 or 15 minutes with a brief informational phone interview.
The purpose of an informational interview, or any networking conversation really, is to let someone know that you are looking for a new challenge in your career. The more people that know that you are looking for a position, the faster you will find a job.