Since this old, misguided thread still appears on google searches when the subject comes up. Nothing would be more fair than to bring a proper perspective to it.
It is awfully naive to say that pinterest wont forge traffick because it would be illegal, when tech giants are no strange to criminal activity, most, are, in fact, always doing things that are still criminal or would be, it they werent in bed with the goverment (like facebook).
This sort of person must be the one that would trust when they say "we respect your privacy".
Not to mention things that are simply embarrassing lies, like when reddit claimed to have more users in the united states than the population of the united states.
Pinterest in particular is known to publish advertisements with phising links and fraudlent stores in general. It is also known that even when you specificy a particular country to advertise to (even if exclusively), they will send traffick from different locations to eat up your budget as fast as possible.
There were also complaints from those who linked their websites to pinterest, in which pinterest claimed that several of their sales were obtained through their ads, when in reality the clients were already long time clients, obtained through different means, and not at all related to the ads. Such thing will cause pinterest to look far more effective than it is when it speaks about cost/benefit.
It is not strange to think that most of the traffick from their ads comes from bots. Many claimed that the majority of their traffick from pinterest will display the behaviour of a bot.