why is the sky not violet

After reading this xkcd strip I wondered the same thing. Off to my favourite activity: seach the internet for answers.

The sky is blue because:
1) Shorter wavelengths are scattered more (Rayleigh scattering) than longer ones and therefore the radiation that reaches use is shifted to the blue-violet part of the visible spectrum.
2) But our eyes see better towards the middle of the visible spectrum and can't see the violet as well as the blue.
And therefore the sky looks blue to us humans.

Source:
http://www.msnbc.msn.com/id/8631798/
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter19/rayleigh.html