Ads are among the most benign things someone could use your private information to do. With your personal information:
* Parties can engage in price discrimination against you. (You don't shop around? you've got some extra spending money? double prices! Looking up risky activities? high insurance rates!)
* Parties can engage in lawfare and blackmail
* Parties can influence elections (without advertising, e.g. by gerrymandering or by targeting your participation in elections just based on knowing how you'll vote)
* Parties can target people of your race or beliefs for genocide (oh, sorry, I meant to say "lawful orders of governments")
Plus the definition of advertising itself is up to interpretation: is sending someone to your door advertising?