Are there any good solutions for that, preferably covering as many countries as possible? For example, I am pretty sure that for Germany the standard "credit card check" is insufficient, as the law will just argue that "the child might borrow the credit card". Would it be sufficient for the USA, and is there a way to check the country of origin that our users are coming from?
I believe they must have used a product like ChoicePoint's Age Verification (http://www.choicepoint.com/business/financial/ageverif_fs.html). Basically a database of public records.
Hope that helps, Wayne Chang
Personally I would consider credit card ownership as sufficient, as I think they are only handed out to adults? If a kid steals the credit card it is probably so spoiled already that some erotica won't do much further harm... But the law doesn't agree everywhere.
In general there is almost no practical way to verify age. Credit cards are the best filter, and even that has flaws.
Have a legal disclaimer that must be accepted before any content is available (cookie-based). Ensure your obeying your local laws regarding distribution of pornography.
Sorry, this is more of a legal, rather than technical question. Did you do a google search? http://www.idology.com claims to have something.
It is of course a legal question, but also a technical one. For example it is a technical question if I can determine the country my user is coming from. I suspect not, though (user could use proxy in other country) - or at most, one could determine a probability and then it would again become a legal question.
You make a good point about proxying through different countries, but I don't think in you would be liable for that. Often these things work on some sort of a "reasonable effort" type clause, because its impossible to verify with complete certainty someones age programmatically.
Perhaps asking them trivia about music that was in style two decades ago...