The rise of in-store mobile commerce | Pew Research Center's Internet & American Life Project:
More than half of adult cell phone owners used their cell phones while they were in a store during the 2011 holiday season to seek help with purchasing decisions. During a 30 day period before and after Christmas:
38% of cell owners used their phone to call a friend while they were in a store for advice about a purchase they were considering making
24% of cell owners used their phone to look up reviews of a product online while they were in a store
25% of adult cell owners used their phones to look up the price of a product online while they were in a store, to see if they could get a better price somewhere else
Taken together, just over half (52%) of all adult cell owners used their phone for at least one of these three reasons over the holiday shopping season and one third (33%) used their phone specifically for online information while inside a physical store—either product reviews or pricing information.