Social networks were buzzing over the weekend about Black Friday and Cyber Monday at a rate roughly 51% higher than a year ago, according to new data released by Salesforce.com Inc.

The report suggests there were about 934,000 mentions of Black Friday and Cyber Monday in the 30 days leading up to the day after Thanksgiving up 50.8 from 619,558 in 2015 and 78.9% more than the 522,000 mentions of those retail events in 2014.

Amazon.com Inc., No. 1 in the Internet Retailer 2016 Top 500 Guide, was the most-mentioned retailer with 27,413 mentions thanks in large part to its Black Friday Deals Week campaign, Salesforce says. Amazon had 13.1% more mentions than the next most-mentioned merchant, REI (No. 74 in the Top 500), which received 24,238 mentions. REI for the second straight year highlighted its decision to close stores on Black Friday with its #OptOutside campaign that encouraged consumers to spend time outdoors.

The report found a marked shift in consumer sentiment before and after Thanksgiving; the majority of those posts—78.6%—were positive in sentiment leading up to Black Friday, but after the holiday that share fell to 72.7%. That may have been the result of heavy web traffic resulting in glitches for some retailers on Black Friday, most notably at Macy’s Inc. ( No. 6).

At the same time, the element of surprise helped some retailers garner positive buzz on Black Friday. For instance, Sephora USA Inc. (No. 129) launched an unexpected flash sale on Friday that helped it garner 26,183 mentions, which was behind only Amazon, Wal-Mart Stores Inc., Best Buy Co. Inc. and Target Corp., Salesforce says. That marked the first time Sephora has ever been among the 20 most-mentioned retailers since Salesforce began tracking social buzz.

Some retailers garnered attention online by boosting their advertising spending, especially on mobile devices. From Monday through Sunday, year-over-year spending on mobile ads among Chacka Marketing clients rose 202%, compared with a 33% increase for desktop ads, says Casey Wilson, the marketing vendor’s vice president of digital media. Those gains produced the desired the effects as mobile revenue rose 65% compared with an 8% increase on desktops.

Mobile’s share of total advertising spending rose significantly to 35% from 19% last year. Desktop budget allocations decreased to 52% from 64% of total budgets in 2015. Tablet budgets also shrank to 13% from 17%.

“Our teams have also noticed a significant increase in Thanksgiving Day spend and traffic this year compared to last,” she says. “Year-over-year costs, conversions and clicks all increased at comparable amounts on Black Friday. We fully anticipate a lift in Cyber Monday conversions as a result of the increased click traffic, year over year, on the days leading up to the largest online shopping day of the year.”