Not sure if it is good form to revive old threads but I stumbled cross this one the other day, while waiting for some prints to wash. At the time I pretty much agreed with the advice that had been given, basically that if the person in the image is unrecognisable then there is no need for a model release. At about the same time Twitter were using an image on their front page of three guys in India playing cricket with the Taj Mahal in the background. It was a colour twilight shot with the cricketers in shadow, but not total shadow their bodies were probably rendered at about zone 3, and their heads had been burned in to total black, rendering them unrecognisable in terms of a model release. I thought nothing more about it and considered it fairly standard usage of a captured street image. Fast forward two weeks. I wanted to upload a video to You Tube, now part of Google, for my girlfriend I did not have a You Tube account but I did have a Google account which I use to manage both our websites Google presence. I used my Google user name and password to login to You Tube and I logged in but was asked to confirm some additional details that I had not been asked for on any previous use of my Google account. I entered false information as I don't think the requested information was any of Googles business and I had been perfectly capable of running the account for the last three years without Google having that information and it was just part of a great data mining exercise on Googles part. The information I entered was that my year of birth was 2012. Google immediately locked my account as it rated me as being under-age to manage a Google account and demanded that I send my credit card details or post them some government backed ID before they would unlock my account. I cannot now manage my, or my girlfriends, web presence, thankfully I don't use g-mail as my main e-mail account but I am bloody furious with them and will not use their services again. So what has this got to do with the OP? Google, Facebook, Twitter and the rest are now vast global corporations. The image used by Twitter may not have been recognisable to the majority of the global population but it would have probably been recognisable to the people involved in the image, “Remember that day we were playing cricket and the tourist with the expensive camera stood about taking pictures?”. You can picture it now, it is sunset you are in an Indian suburb near the Tag and you see some guys playing cricket great shot you think and take it. You post it to one of the online stock sites with the faces suitably burned in to avoid the need for a model release. If I was one of the guys in the image and that image had been used to promote a vast global entity while I was being denied access to that entity I would be livid. I know you will say Twitter is not Google or Facebook but all of these organisations operate on the same model of data mining their users. How would you feel if you found yourself promoting an organisation you were morally opposed to even if most of the rest of the world didn't know it was you? One further thought, I used to be involved in events tat were sponsored by Microsoft. Mine was a technical role and I am not an Equity member ( the UK actors union). On one event Microsoft had employed a film crew to film the event for promotional usage, this had happened on a couple of occasions and generally didn't involve me. On this particular occasion the director swooped down and announced that someone would hand me a memory stick and I would put it in the computer (a mac) and they would recreate the download. I pointed out that I was not an actor and did not want to be in their promotional video because I did not agree with Microsofts licensing agreement “But It's going to be viral” (something to do with the internet) they said. I repeated my stance and after the ten minuets it took them to get their heads round the concept that someone may not want to promote their products, especially without being paid, it was decided that the sound engineer would play my part.
Now I don't want in any way to stop photographers, professional or amateur, taking photographs of anyone in a public place. But I do think that in this day and age we need to think more carefully than ever what we do with those images. Personally I find it hard to photograph someone without there explicit consent such as in a formal portrait, or hiring a model to get a shot, and even then I wrestle with my interpretation. But that's just me.
One very last thaing http://www.duckduckgo.com/ not google for untracked surfing