[blawa]

Can you explain what you're talking about? Do you mean that if a program exhibits bugs only under a certain condition that its bugfree? And even assuming you know the spam's distribution, the error function needs to heavily penalize any false positives. So even one occurrence is a major event. Your comment reeks of blind faith, not appropriate for a forum like this

[scardine]

It is not blind faith, it is the f*ing scale. It is hard to argue that one occurrence is a major event when you are at the size of gmail.

[jacquesm]

It's never one occurence.