NYTimes.com’s “Bits” blog, citing Nielsen Mobile data, reported that 3.6% of all mobile phone users in the U.S. – about 9.2 million people – have shopped online via their phones.

That number is expected to grow dramatically in the future, according to Nielsen Mobile’s study, which found that about half of all consumers who transmit data via their phones anticipate making a “mobile purchase” in the future.

But some consumers are steering clear of shopping online by phone — at least for the time being. More than 40% told Nielsen researchers they were wary of security risks associated with such purchases.