Get ready for ads to start addressing you directly by name and doing other like things to get your attention. Google isn't usually _too_ overt about these sort of things but the less savory ad networks could get really unpleasant. "Hey there George Thompson, click to see one weird trick to hide your arrest records from your wife Mary"
As another posted commented, there will be a minimum list size to prevent this sort of thing. For example, Twitter already allows targeting to specific individuals, but the list minimum is 500 (if I'm not mistaken).
def scumbag_targeted_campaign_builder(accounts):
for name, users in groupby(accounts, key=lambda x: x['first_name']):
users = list(users)
while len(users)
Some variation of this is pretty easy, and likely will become common.