Possibly a variant on the old "You need to update your Wells Fargo (or wherever) account information" scam. They blast it out to a zillion people at random, many of whom don't even have accounts at Wells Fargo. That doesn't matter -- many of them do. And of those who do, some will be naive enough to follow the link and hand over their credentials.
It's entirely possible that a scammer would exploit a real large-scale cancellation by sending zillions of fake cancellation messages. In fact, that would make the scam work better. If the intended victim a) has an AdSense account and b) has heard of the (real) cancellations, he's probably going to be much more likely to click on the fake cancellation message.
