I don't have the time to wade through everything Don Marti and others have written about the 'evilness' of targeted online advertising. However, I do think they are correct to worry about it. As a marketer, I'm most concerned with the plausible idea that it causes people to ignore advertising at a higher rate. As a human being, I'm concerned that it may reinforce problem behaviors such as gambling addictions.
Although it will never go away, mass advertising via broadcast media is NOT the answer for any EXCEPT the largest advertisers. However, there's another form of advertising which is not getting much attention is this discussion, and that's sponsorship. Not permanent sponsorship but temporary sponsorship and multiple sponsors who can keep a web site going. Someone still has to sell and maintain those sponsorships, but for niche web sites, this seems a much more useful approach than highly targeted advertising. I hope to see it flourish and slowly reduce the amount of mechanically targeted ads chasing us around.
Don Marti blog: Targeted Advertising Considered Harmful, Updated 2015-May by Don Marti
In a market with asymmetric information, signaling is an action that sends a credible message to a potential counterparty.
Advertising spending is a form of signaling that shows that a seller has the money to advertise (which the seller presumably got from customers, or from investors who thought the product was worth investing in), and believes that the product will earn enough repeat sales to justify the ad spending.