Look at all the top advertisers on the internet, in almost every case it's all big brand advertisers that can't prove results, like Nike for instance. I know someone at Nike who held a marketing position there: she said, basically they just throw the money out there and hope that it works. There's very little validation that any of it works. And, I've heard on an NPR show how a lot of big brand advertisers are just continuing to do what they've always done because they've been doing it so long.
Now, the economist of course would say that companies who squander money on advertisements would loose market share. That's the way it should work. But our capitalist markets aren't nearly as efficient as people commonly believe.
On a personal note: I can tell you 99.99% or more of the advertisements don't work on me at all. How do i know this? I keep close account of everything I spend money on. I once did an audit on everything I've spend money on in the last 3 years and found that almost everything I spent money on is not due to ads (with the exception of SEO ~ I do occasionally find products through search engines but this usually isn't considered a direct advertisement expense). It's not that I'm against ads. If an Ad promised a product I actually wanted (say a home at an affordable price, or a faster way to get to work), I'd buy it in a heartbeat. The problem is, everything that's being advertised is more stuff I don't want.