While a Web presence is a prerequisite to doing business in the 21st century, the fact that 77% of consumers are now using tablet computers or smartphones to shop is forcing retailers to rethink their digital strategies, according to a survey from online price comparison engine PriceGrabber. Realizing this is not a decision to be taken lightly, retailers need to take steps to ensure that mobility can be an opportunity, and not a threat, to their business.