Very interesting debate this one (And BTW that Spanish age one is scary....)
My opinion is that I feel an age law is appropriate for a matter like this, however what really gets my goat up about the UK in particular (perhaps Europe wide is the same never really looked into it) is why we have different ages for everything... So I could have "Legal" sex at 16, Couldn't drive till I was 17, Couldn't vote till 18 or Drink till 18, oh but I can smoke at 16, Buy a Lottery ticket at 16...and give my own medical consent at 16, oh but cant give blood till 17! Here's an idea make it one flowering age!
Ok back to the thread in point, I think I'm more on the Goku's side in this one, the 16 rule is a little grey when it falls to a 16 yr old & 15 yr old and allowances should be made for that and of course if 2 pre 16 teens feel they are capable of making this decision then by all means go ahead. The "No" go area and where the law should apply from perhaps is that once you turn 18 it is THEN illegal for any 18+ person to lawfully engage in activity with an under 16 as that is when the age gap becomes more obvious. And as Goku put it, imo I see no reason a 20+ year old would have those sort of feelings for an KNOWN under 16 anyway.
Now of course on the slight devils advocate, we've all been out on nights out and I can count numerous/hundreds of times I've seen people of a YOUNG age in Night Clubs etc. (some are obvious to tell they are under 16, others perhaps not so, my best friend back home could pass as an 18 year old easy from the age of 14) if they then lie about thier age at the time, how does that fit in with said law?