Right on about Need vs. Awareness .... Think of Coca-Cola or McDonald's, or even Budweiser. There are many large companies that use TV/Internet to keep their brand strong. Everyone knows about these brands, there is no direct "need" for any of their products (one could argue against this but I digress), but they need to keep advertising so when you are hungry, or thirsty, or sober you turn to them first.
That´s right, I think there´s also a hybrid, probably like banner advertising, google adwords, amazon recommendations and gmail, which is showing you ads for things you might be interested in but not necessarily actively seeking.
When you see an ad for coke on the street there is just some probability you are thirsty or will remember coke when you become thirsty, with adwords and other kinds of contextual advertising there is also a probability you might be interested in what the advertiser is presenting you, so they might just hit a need or making you aware of it, and not really creating it as in creating demand.
