Primary down, all things gone haywire?

What happens if Primary went down while data not replicated to secondaries? Read the following:
http://aphyr.com/posts/284-call-me-maybe-mongodb

Solution might be "WriteConcern.MAJORITY", but it does raise concern with performance.

6000 total 5700 acknowledged 3319 survivors 2381 acknowledged writes lost! (╯°□°）╯︵ ┻━┻

See this? (╯°□°）╯︵ ┻━┻

I thought it was funny animation..