It's michaelochurch's rating system for programmers:

http://michaelochurch.wordpress.com/2012/01/26/the-trajector...

I've never seen it used by anyone other than him either.

Roughly speaking, it represents the transition from an adder to a multiplier. A 1.0 programmer is competent at "adder" tasks (scripts, bug fixes, features) but not yet ready for infrastructural work. A 2.0 programmer is highly competent as a multiplier. It goes from 0.0 (complete beginner) to 3.0 (global multiplier) but most (probably 99%) professional software engineers are between 0.8 and 2.2, with a median around 1.1-1.2.

This is more up to date than nostrademons's link:http://michaelochurch.wordpress.com/2013/04/22/gervais-macle...

Also, from Quora: http://www.quora.com/What-do-the-top-1-of-software-engineers...