For government, pornography is emerging as a key skirmish in this fight. David Cameron wants to stop underage users accessing porn online. This will require a government-approved age-verified ID system: a significant step towards cementing our online identities. 

Cameron’s Home Secretary is way ahead of him: Theresa May’s Investigatory Powers Bill will force internet companies to keep records of customers’ web visits for up to a year. Why? Because those internet companies’ customer records provide a vital link between behaviour and identity.

Rights holders, too, see gains in pinning down who’s who online. The BBC is reportedly mulling the introduction of login access to iPlayer services. Yes,it could help enforce licence fee payment, but it would also link iPlayer users to a their real-world identities.

But by far the biggest beast in the fight to concretise online identity is Facebook. Arguably it knows more about you than your partner does, and that’s a powerful tool in ID verification. No wonder then that the web is littered with prompts to "log in using Facebook". The Palo Alto giant sees itself as a prime mover in ID management, a thriving market among the world’s governments and corporations. (Handily it also helps advertisers, who fund Facebook, to get a handle on what products you might like).

 You are one person, according to its boss Mark Zuckerberg, you should have one Facebook account, the real you. As its terms state: "Pretending to be anything or anyone isn't allowed". Think of that phrase next time you see a carefully-posed selfie.

 Zuckerberg might feel differently about confirming identity if he was a gay man in Saudi Arabia or an anti-regime journalist in China.

 The drive to ‘fess up to who we are online throws up problems in other areas, from transgender social network users being told their usernames are invalid, to the debate over the male/female binary on many government fill-out forms.

 I have more prosaic reasons for opposing rigid identity management: much of the work I do online is done "undercover", ie. through fake identities. It may sound glamorous but it’s mostly hard, grinding work and psychologically uncomfortable for me and those I love. Nonetheless, the use of subterfuge (under strictly controlled conditions) is sometimes part of the job,and I feel the job is important enough to merit it when investigating and exposing criminality and wrong doing. If I had to be honest about my identity online at all times, I’d be out of a career. 

And all around, I see a growing counter-culture in which identity remains flexible. It exists not only the chat-rooms and forums, but in attempts to subvert mainstream services, such as the secretive Alt Twitter movement in which users of the social network create closed groups of anonymised profiles.At an event I recently met three pensioners who delighted in the fact they had obscured their real identities on Facebook: their "undercover" lives gave them a sense of naughty freedom. 

If this counter-culture had an HQ, it would be the dark web. At its heart is a technology that preserves users’ anonymity while still allowing them to use the internet’s architecture (it will therefore circumvent Cameron’s porn crackdown at a stroke). 

The dark web is a world of transgression; people often perceive it as"the place where you can buy drugs online". There’s no denying that cybercrime has thrived in this virtual masked ball. 

But here’s the bit most people don’t encounter: online crime is a business,and the dark web’s crooks face a unique challenge as they buy and sell illicit goods: how can commerce exist when traders do not know with whom they’re transacting? 

The techniques used in crime forums to tackle this challenge are a fascinating glimpse into an alternate universe: where trust can be faceless. I have seen markets for stolen credit cards which offer an escrow service to give buyers confidence that their order will be filled. One of the most active hacker forums assigns each member a reputation score, supported by a system of "vouchers" from other members: the higher the rep score, the more reliable the member. 

Fascinating as find this world, I deplore the web of high-volume, low-margin criminality that I see it creating. Yet faced with the cynicism of commercial and governmental interests in defining who we are online, I can’t help but pine for an online space in which identity is still something we, the users, can control as we wish.