[algolicious]

Facebook's testing practices and culture of developer accountability help to prevent serious bugs from being rolled out in production code. When a developer's code disrupts the website and necessitates a post-deployment fix, the incident is tracked and factored into Facebook's assessment of the developer's job performance.

[...]

Employees with low karma can regain their lost points over time by performing well—though some also try to help their odds by bringing Rossi goodies. Booze and cupcakes are Rossi's preferred currency of redemption; the release engineering team has an impressive supply of booze on hand, some of which was supplied by developers looking to restore their tarnished karma.

This sounds like Facebook strongly rewards developers who work on trivial, low-risk features rather than larger, more important features. Also, it sounds like bribery factors into your overall job performance rating.

[nbm]

Push karma primarily affects how likely the release engineering team will accept any breaking of the standard rules of getting your code into the push. It generally doesn't drop if you are responsive and responsible for any problems your change causes. The only way to restore points is to show respect and consideration for the hard work the release engineering team does.

(I'm not 100% sure, but I think most of the booze and cupcakes come from people who were appreciative of the release engineering team for bringing potential issues to their attention or for being accommodating in terms of hours and in terms of delay to get things fixed.)

Being irresponsible (not supporting your changes) will factor into your performance review, but working exclusively on low-risk features will most likely hurt it way more.

[binxbolling]

I think you're reading too much into that part.

[Spellman]

I was more annoyed that the karma system wasn't attributed to other sites who used it first. Which is to say not terribly.