You may have read about Tangou - like minded individuals combining to specifically collectively haggle for an item. Popular in China where haggling and collectivism are both salient.
Similar thing with carrotmob - who seek to combine individuals to reward companies and stores that are green - even liquor stores. Good video example here.
Both examples of social shopping using technology to facilitate grouping of people for a specific purpose.
The TNS survey cited earlier indicated that Canadians are more open to this than shoppers in other countries ...although little sign of it here so far.