When are consumers willing to share their data? How much data? If you don't realize it already, Europe typically leads the way on data and privacy issues. Their laws are much stricter and they are much more critical of data capture methodologies. North America tends to lag quite a bit and we have much more of a laissez-faire attitude - often collecting too much and doing too little with it.
Consumer willingness to share information with brands has rocketed in the past 18 months. The latest research shows an increase from last year indicating good news for marketers who seem to be gradually winning the confidence of consumers. (From the DMA's Data Tracking Report for 2012)
This report and infographic are encouraging since they are providing evidence that there's a growing willingness of consumers to share their data. The report shows that, when best practices are utilized and consumers are provided the marketing they want - data exchange is much easier.