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Consumers spent $21.7 billion online (excluding travel and auctions), in the U.S. in the first 50 days of the holiday seasons - Nov. 1 through Dec. 20 - or 26 percent more than the year-earlier, according to comScore.

Among the e-commerce trends this holiday season are increased traffic to retail sites from social networks and blogs; increased sales of luxury items; a longer shopping period; and the emergence of the long tail of niche sellers, according to a Christmas Day rundown by IDG News Service.

The IDG article points to findings from Compete Inc. that social networkers give more weight to peer feedback than to any other information source, and early December stats from Hitwise that online retail sites were receiving 6.2 percent of their traffic from social-networking sites - compared with just 2 percent in the year-earlier period.

In the past, online spending slowed as Christmas approached, but this year it increased 35 percent between Dec. 18 and 20, according to comScore, in large part because, according to Shop.org,  the number of retailers guaranteeing that standard-shipping orders placed by Dec. 18 or 19 would be delivered by Christmas Day nearly doubled from last year.

The fastest growing category is jewelry & watches, with spending up 66 percent compared with the year-earlier period, comScore said. Spending on other pricey items is also up, including videogame consoles (54 percent) and consumer electronics (33 percent).

Blogs and search engines are credited by research from MIT's Sloan School of Management and the Univ. of Maryland for the growing online opportunity for niche sellers; because web facilitates the bringing together of  buyers and sellers, manufacturers of unique, niche products feel inclined to develop and sell them.