Ads are sort of also 1:1, in the sense that you have to pay for them to be shown, and the number of impressions is proportional to the price. You could argue USPS is more expensive in this regard, but they'd be quite happy to accept your election ads and stuff them into my mailbox, for a fee. In fact, they do this pretty much all the time, and political candidates, at least where I live, don't put a single word of truth about their opponent on the leaflets.