Product tampering includes both random mass poisoning and the deliberate poisoning of food and drugs as an instrument in commercial blackmail. It is a modern phenomena born in 1980s.
The first case of mass food tampering was in 1982 in USA, when four people died after swallowing the pain-relief drug Tylenol, laced with cyanide. There was no blackmail, no claim of responsibility and no arrest.
To poison food is to break all the taboos about what is natural and good. Our dependency on pre-packaged and hygienic food has made mass poisoning possible. From the criminal's point of view, it has the merits of anonymity and remoteness: he need never come into personal contact with his victim.