Even more offer product recommendations, according to Top 500 data, but some retailers may be holding off deploying personalization and recommendation technology.

E-retailers’ efforts to make online shopping more personal may have hit a speed bump, suggest preliminary data from the upcoming 2014 edition of Internet Retailer’s Top 500 Guide, which ranks web merchants by revenue.

The data so far show that 77% of web merchants in the upcoming guide offer product recommendations, nearly the same as the 76% in the 2013 edition, according to Top500Guide.com. Roughly 49% of merchants in this year’s guide offer personalization to online shoppers, up slightly from the 47% who offered it last year.

The data could indicate that personalization and product recommendation technology “has just become mature at this point and the holdouts are holding out for a reason [such as] budget and resources,” says Forrester Research Inc. analyst Sucharita Mulpuru.

Select retailers listed as not offering product recommendations or personalization did not immediately return requests for comment or declined to comment. But some major retailers are seeing the value in making their online shopping experiences more personal. As part of general e-commerce upgrade over the past year, Staples Inc., No. 2 in the 2013 Top 500 Guide, has been rolling out faster, sleeker and more personalized desktop and mobile sites. For instance, the office supplies chain is making its mobile sites and apps more relevant to shoppers by welcoming mobile customers with information about reordering items and product recommendations based on their past shopping histories, says executive vice president of global e-commerce Faisal Masud. Previously, Staples would first try to promote its store locator or rewards program.

The rise of the shopping across multiple devices also presents obstacles to retailers hoping to beef up or deploy personalization features, Mulpuru says. For instance, a shopper might start browsing products on her PC at work, switch to a smartphone for the train ride home, then finally make the purchase at night on the couch using a tablet. Retailers struggle to follow the shopper as she moves from one device to another. “There’s a lot of challenge to creating profiles of shoppers because of device fracturing,” she says.  “You really can only personalize accurately with same-session information, and it gets more complicated trying to take other history into account because devices haven’t been tied together.”