Ads are almost never how informed purchasers make decisions. In the age of the Internet, review systems (whether collaborative or curated) are infinitely better sources of product information than ads. They are also vulnerable to manipulation from would-be advertisers, but less so (and any influence can be mitigated by trusted reviewers).
Ads do tell you something about a company though. Like, do they waste a lot of money on marketing? Have a good sense of humour? Target my in-group as a customer? Pay attention to detail?
