I had an eBay transaction go very wrong. Foolishly I used my real email and domain for communication, with a very WHOISable home address.
When the physical threats started I had to get the police involved.
There's also the issue of pseudonymity. If I work on a lot of different projects, I don't necessarily want everyone to know about everything I'm doing with everyone else.
This doesn't mean I ignore NDAs and share sekrit stuff - I most certainly don't. But I've freelanced in the past, and some employers have strange and unrealistic expectations about how much exclusivity they're buying.
This isn't hypothetical. In the past I've been told "You absolutely can't work for anyone else if you freelance casually for us."
Really? How about "no"?
Also it's better for free speech. I can express opinions freely with online privacy. I don't necessarily want those opinions to be associated with - say - a startup I'm creating.
Generally, contact info is a problem. It's actually mandatory for UK companies to include a business registration number and an office address. (I'm not sure how many UK devs know that.)
Problem is, when you can incorporate in Delaware or Kiev, physical contact details start to become meaningless anyway.
My rule now is that contact is easy if there's a networking, customer care, or community-building benefit. But privacy is a fine thing too.
Being able to pick and choose is best of all.