Nearly half of all Internet users worldwide will make online purchases this year, according to IDC data. Furthermore, by 2012, more than one billion online buyers will complete business to consumer transactions totaling about $1.2 trillion, according to IDC's Digital Marketplace forecast.

Business to business eCommerce will be ten times larger, amounting to $12.4 trillion in 2012, the study finds. Moreover, 30 percent of the world's population, which amounts to about 1.9 billion unique users, will use the Internet four years from now, up from about 1.4 billion people, or about 25 percent of the world's population this year.

What's more, the number of devices accessing the Internet will double to more than three billion by 2012. That's up from more than 1.5 billion this year. Half of those devices will be mobile devices, IDC says.

"The Internet will have added its second billion users over a span of about eight years, a testament to both its universal appeal and its availability,"

said John Gantz, chief research officer at IDC. "In this time, the Internet has also become more deeply integrated into the fabric of many users' personal and professional lives, enabling them to work, play, and socialize anytime from anywhere. These trends will accelerate as the number of mobile users continues to soar and the Internet becomes truly ubiquitous," he predicted.

Once on the Internet, users will continue to spend time on basic web activities, such as searching, shopping, and sending email, according to the IDC forecast. But more advanced Web 2.0 activities, such as watching user generated videos, posting blogs and participating in social networks, are capturing the attention of increasingly more Internet users. These more advanced functions create new opportunities and challenges for online advertisers looking to capitalize on Internet advancements.

Following are other findings based on the IDC forecast:

• China's online population, which exceeded the U.S. online population in 2007, will grow to 375 million users in 2012, up from 275 million this year.
• Roughly 40 percent of all Internet users worldwide have mobile Internet access. The number of mobile Internet users will reach 546 million this year, nearly twice as many as in 2006. That number is expected to surpass 1.5 billion worldwide in 2012.
• Worldwide spending on Internet advertising will total $65.2 billion this year, which represents nearly 10 percent of all ad spending across all media. This share is expected to reach 13.6 percent by 2011, as Internet ad spending grows to $106.6 billion worldwide.
• The most popular online activities are searching the web, finding information for personal use, using Internet email, accessing news and sports information, and accessing financial or credit information. In addition, more than 50 percent of online users worldwide are using instant messaging and playing online games.
• Among mobile Internet users, the most popular online activities are searching the web, accessing news and sports information, downloading music, videos and ringtones, instant messaging and Internet emailing. By 2012, downloading music, videos, and ringtones will have become the number one activity of mobile Internet users worldwide.