Indeed and people often say "if an ad is annoying I'll never buy that product, so ads don't work on me, also they've never made me run out and buy something" !

However advertising is accompanied with thorough independent market research and sales numbers and companies can directly see the impact of their ad campaigns. It's indisputable.

In the long term it's also about brand recognition, we see a "stupid ad" today and in a year when we're looking for that kind of thing we are more likely to choose that brand over another and we don't know why but "this jams seems better". The effect is proven, scary and it's something we're relatively helpless against. It doesn't help that our brains sometimes register things running in the background on the TV while we're petting the dog. Product placement in movies works like that too, if we notice it we think it's obvious and stupid, but we still notice it and even when we don't notice it our helpful subconscious is right there helping us remember.

Moving into even worse territory, on social media like Facebook they can profile us enough to know where we're leaning politically and if we're not entirely confident in our political stance they can show us ads that looks like product ads but are designed to nudge our political stance a bit to the side in the desired direction.

The effect of ads on the subconscious is scary. It's not mind control but it's can influence us.

Not on social media ? No problem, they still build up shadow profiles. A Google executive once bragged at a conference that they know everything we've done since the first day we got on the Internet. Hyperbolic maybe but that confidence comes from somewhere.