Online US holiday spending from November 1 through Christmas Eve 2009 reached $27 billion, a 5% increase over the same period a year earlier, according to comScore. Consumer electronics led among product categories, recording sales growth of 20% over 2008 levels.

For the period from Black Friday through Christmas Eve, and after adjusting for the additional shopping day in 2009, sales grew approximately 3.5%.

"Online sales growth this year was driven by a continued increase in the number of people buying online, but consumers' economic challenges resulted in a slight decline versus last year in the amount spent per buyer," said comScore Chairman Gian Fulgoni.

"This was also a year when retailers substantially boosted their use of social-network marketing and the larger retailers significantly outperformed their smaller brethren. In these tough economic times, the retailers with sufficient financial resources and a willingness to invest in aggressive marketing and free-shipping offers were clear winners."