More than two-thirds of US online buyers who participated in the USC Annenberg Center for the Digital Future’s study
in 2007 said that their Web purchasing reduced their retail store purchases, up from the 65% who said so in 2006.

US Online Buyers for Whom Online Buying Reduces Offline Buying, 2006 & 2007 (% of respondents)

That does not mean that online buyers always avoid making purchases offline.

Web buyers spent
an average of $511 in stores compared with $313 online in a three-month period during Fall 2007, according to Forrester Research "Retail Channel Surfers Prefer to Buy Offline" report, as cited in Internet Retailer.

But online was far ahead of other channels such as catalog, phone and TV shopping.

Average Cross-Channel Spending by US Online Buyers in the Last Three Months, by Gender, 2007

Web merchants are getting better at retailing physical products on
their sites, and product information is now available at review, social
networking and other sites, which helps explain why buying goods online
has become so popular.

Different purchasing channels have traditionally offered different benefits, as detailed in the e-tailing group‘s "2006 Transformed Multi-Channel Shopper" report, conducted with J.C. Williams Group and StartSampling. Consumers surveyed expressed a preference for stores for the social experiences available, and catalogs for portability.

Yet social shopping
sites bring a social experience to Web shopping, and the popularity of
laptop PCs has made retail e-commerce a more portable experience.

Reasons that US Consumers Prefer to Shop Online, in Stores and/or via Catalogs, 2006

This is all straightforward good news for pure-play online
retailers. But multi-channel retailers face a question: if buying
online reduces in-store purchases, how exactly should the two channels
work together for consumers?

Via eMarketer