This is old news, but sometimes we need to be reminded that even in countries such as Sweden (and Denmark) there have been examples recording the life of children during 15 years without them knowing. There was a bit uproar when it came out in 1986 that 15000 children born in 1953 were tracked…
Listen to the P3 documentary (Swedish) if you missed this, or just are interested to know more about the motivation behind this study.
Read the report here in English.