[1letterunixname]

Actual referrals for specific needs are useful. Letters of recommendation are variably useful, but not warm intros.

Social media-based "networking" in the industry has limited utility. I was 1-2nd degree on LI from most of Silicon Valley but with 100's of people I never talk to.

You're barking up the wrong trees combining outbound effort that has much less value, especially if it's untargeted or unfocused. In general, it's better to market yourself and let the hiring managers and headhunters find you. Although, it's entirely possible to replace the role of the headhunters if you market and convey useful business value you present to prospective employers: a cover letter exists to sell a resume to sell a phone call and so on.

If you're trying to network for work, I would check out hot and interesting tech meetups.

Remember, it's sales and dating, and therefore, a numbers and interest game.