Probably not directly, but I can't imagine what purpose this would be except to sell ads. That's what Facebook's business is all about.

I wouldn't be surprised if they were trying to run some sort of regression of behavior against bank balance and debt load. So sure, they're not using your bank account for ads, just a proxy of your bank account for ads.

Finding proxies for income is decades old (zip code and magazine subscriptions being the classic example), but I'm not aware of anyone doing at this scale and with direct input from banks as opposed to volunteered information.