Does networking really help people find jobs?

People say that it is a good idea to network.

Many of my friends tried it. Some of them are actually quite persistent. Most, if not all, of them are unemployed or underemployed.

I tried networking. Many of the professionals I speak to are very busy. Some would answer questions I send them to follow-up on our conversations. Others would ignore my follow-up email altogether.

So, in your experience, does networking actually work?