Google Adwords have recently announced that you are now able to target people by uploading a list of emails so that your adwords are served to those who are logged into their gmail accounts.
You will now be able to set bids and tailor the ads to your target audience. You can also bring Google up alongside the likes of Facebook and Twitter who allow you to target custom audiences. This can only be a good thing because it will allow customers to have much better conversions and more sales for their advertising budgets.
How this would work is the retailer would create a list and then create a search network only campaign that targets only the people on this list. The people on list would then see the retailers ads when logged into their Google accounts. Overall this is certainly another targeted marketing method that is likely to obtain some good results.