South Africa, Sept. 10 -- One of the most dangerous moments in performance marketing is when a campaign begins to look almost too good to be true.

Cost per lead falls sharply. Conversion rates climb. Volumes accelerate. The algorithm finds more of whatever you asked it to find, and the dashboard starts producing the type of numbers that make everyone in the meeting happy.

However, sometimes the correct response to extraordinary performance is not celebration; it is suspicion.

We recently encountered precisely this situation at Offernet while analysing a pet insurance campaign. A very large proportion of the campaign's leads began arriving through third-party app placements at a fraction of the cost we would normally expect from Faceboo...