Official title: President of Clarium Capital Management
Secret identity: PayPal Mafioso
Made wealthy when eBay bought PayPal in 1999, the former PayPal CEO was an early investor in Facebook and runs his own $3 billion hedge fund. He's also capo di tutti capi of the PayPal Mafia, whose members went on to fund and/or launch some of the most successful companies on the planet (YouTube, LinkedIn, Yelp, Flickr, and Digg) and beyond (SpaceX).
Why you shouldn't mess with him: Because he can make start-ups an offer they cannot refuse.
Jim Q. Crowe
Official title: CEO of Level 3 Communications
Secret identity: Fiber king
When Level 3 completed its acquisition of Global Crossing last fall, it became the 800-pound gorilla of Internet backbone providers, offering more than twice as many network connections as its nearest rival. Via peering and transit agreements, Level 3 provides fiber-optic voice and data connections for thousands of service providers in the United States, Latin America, and Europe.
Why you shouldn't mess with him: If your ISP gets into a spat with a backbone provider--as Comcast did with Level 3 in the fall of 2010--you could find yourself cut off from big chunks of the Internet. Better bring a good book to read.
Official title: Investor
Secret identity: Russian oligarch
The Moscow native created Mail.ru, the most popular website in Russia and the sixth largest in the world, according to Comscore. As founder of the $12 billion Digital Sky Technologies (now Mail.ru Group) investment fund, Milner was an early and influential sponsor of Facebook, Twitter, Zynga, Spotify, and Groupon. He now owns a $100 million home in Silicon Valley and a piece of every startup coming out of the Valley's fertile Y Combinator incubator.
Why you shouldn't mess with him: Those alleged ties to Vladimir Putin? All just Internet rumors, we swear.
Official title: Graduate Fellow at the Center for Applied Cybersecurity Research
Secret identity: Privacy badass
Self-made privacy geek Soghoian specializes in shaming organizations into doing a better job of protecting our personal information, whether he's nudging Google to adopt SSL encryption for Gmail, revealing how often Sprint shared user location data with the cops (8 million times as of October 2009), or making a mockery of the TSA's airport security. Soghoian also briefly advised the FTC on privacy issues until his bad-boy methods rubbed his bosses the wrong way. His latest target? The U.S. Congress and CISPA.
Why you shouldn't mess with him: When Facebook's public relations firm surreptitiously pitched Soghoian on a story smearing Google's privacy practices, Soghoian outed them--giving Facebook an even bigger PR fiasco to clean up.
Black Hat Hackers
Official title: Unemployed
Secret identity: Too many to name
The script kiddies at Anonymous have nothing on the real black hats, whose identities are rarely revealed but whose impact is rapidly growing. Whether they're privateers extorting money from online gambling sites or government agents spreading targeted malware attacks like Stuxnet, criminal hackers can pull off real damage--not just pranks and protests. With vital infrastructure such as water and power utilities run by aging and vulnerable industrial control systems, we all have reason to worry.
Why you shouldn't mess with them: You're kidding, right?
[Did we miss anyone? Nominate your top Web puppeteers below.]
Follow Dan Tynan on Twitter.