Positive feedback

We've all heard the phrase "positive feedback", but I wonder how many of us realise that the typical conversational usage is wrong?

Typically the phrase connotes corrective action taken to restore performance. In systems terms, however, this is negative feedback. Positive feedback makes things worse; it continues an already destabilising trend.

Here's 'positive feedback' correctly used and illustrated, on page 298 of Ian Stewart's wonderful book 17 Equations that Changed the World; the chapter on the Black-Scholes equation. More of which here.