In google analytics what are keywords [not provided]?

[fixxi]

In analytics , organic search traffic, some keywords are shown as [not provided] i.e google does not tell you what keyword was used to land on your page. What/why is that ?

 

[Tigayo]

Re: in google analytics what are keywords [not provided]

How I know Google don't show results for users who are loged in their Google account . It is really a serious problem for me too .
Google do this for some security , but I don't see any secure problem for that .

 

[darkavenger972]

Re: in google analytics what are keywords [not provided]

Upping post since i'm interesting in that too

 

[lavriko]

This are visitors who were logged into google when they visited your website and information about keyword they used to come to your site you can't see. This is a major problem for webmaster these days.