One-trick pony no more: mobile revenue becomes major contributor for Google

Google Android mobile OS is free to license for any OEM who makes phones or tablet computers. Google's business model is to monetize its mobile operating system through advertising:

• Android Market takes percentage of paid apps sales
• AdMob - advertising platform - provides ads for mobile apps and mobile websites
• In addition, AdSense is is optimized for mobile websites
• Google web search advertising is mobile optimized

Google mobile business has reached $1 billion in 2010 and reached $2.5 in 2011. Piper Jaffray estimates the revenue to exceed $4 billion in 2012. I think the trend of 150% anual revenue growth is most likely to continue in year 2012 considering competition is catching up.
Post 2012 Android ecosystem will start expriening growth problems due to

• Increased competition (barriers of entries and swtitching costs are very low)
• Android ecosystem internal problems