I like the description of audience aggregation. I've always felt like advertising based services were thinking the wrong way. It's not that you're finding users (audience) and then monetizing them with ads. Your audience is your product. You could build a big product, a niche product, or a well-defined product. Then, you must sell your product. Your audience is not your customer. They are your product. Your advertisers are your customers.
Do you know those management courses in college where almost everything the professor "teaches" you is common sense?
Somehow this post brought back some memories.