Dive Summary:

• English is still the most popular language online, but the numbers of Spanish, Chinese and Arabic speakers are growing, making international SEO and emerging concern.
• Mobile searches are also growing, particularly in growing markets such as Brazil, Russia, India and China and rural areas without broadband infrastructure.
• A Google report based on search activity at the 2012 Olympic Games in London showed a tenfold increase in mobile searches for related terms during the games' first week.

From the article:

For a long time now English has served as the lingua franca, or common language, of the Internet. English is still the most commonly used language online but it still represents only just over a quarter of total usage.

The growth rates of various foreign languages also far outstrip the growth in English usage, which may be heading for saturation point. ...