Online spending on Black Friday increased nearly 16 percent compared with last year, with social networking sites gaining momentum as a source for shopping tips and mobile devices playing an increasingly important role.

The researcher said that though the percentage of shoppers arriving at retail sites from social networking sites was still relatively small, the phenomenon was gaining momentum, with--not surprisingly--Facebook at the fore. The company said shoppers were using sites like Facebook to find out about deals and inventory levels. It also said the slice of shoppers arriving at sites via mobile devices jumped 26.7 percent year-over-year.

"We're watching online retail, and increasingly social media and mobile, become the growth engines for retailers everywhere, as consumers embrace online shopping not only for its ease and convenience, but as a primary means of researching goods and services," John Squire, the company's chief strategy officer, said in a statement.

Coremetrics pointed to another trend as well, saying "surgical shopping" seemed to be widespread, with people checking out 18 percent fewer products on sites than they did a year ago--an indication that they target a specific product rather than browsing.

And health and beauty, and department-store sites saw encouraging figures. Shoppers spent 17.7 percent more time in virtual department stores, and health and beauty retailers reported a 73.1 percent increase in first-time buyers year over year, and a 53.4 percent increase in the number of visits in which shoppers actually clicked away with a purchase.

Still, online shopping has yet to conquer the cash register. According to the Associated Press, online deals account for between 8 percent and 10 percent of holiday spending.

Update, 2:50 p.m. PDT: Researcher ShopperTrak said Black Friday sales figures for brick-and-mortar stores barely registered an increase over last year, rising a mere 0.3 percent. The company said, however, that the message was mixed because figures for the first two weeks of November were unexpectedly strong--a rise of about 6 percent year over year. "Additionally, a percentage of retailers concentrated on pushing folks to their Websites with various online-only sales, which most likely influenced Black Friday performance as well," ShopperTrak founder Bill Martin said in a statement.