YouTube still hasn't become a profitable business for Google, despite attracting more than one billion viewers each month.

The Wall Street Journal reports that the video-sharing website, which was acquired by Google for $1.65 billion in 2006, made $4 billion in revenue last year - up from $3bn in the previous 12 months - thanks to premium ad platform Google Preferred. 

But it is only roughly breaking even, said one insider, as most users watch its videos when they are linked from or ...