It's a Perceived Benefit which is continuing to be pushed in the hope of revenue down the track when the Technology Grows Up.
Like the Yellow Pages if you are in first you have the Best Placement and these Adds are cheap to insert and are used by those who want the exposure but don't necessarily expect big returns on advertizing.
Or if you like the belief that Facebook is Big so it must be valuable. The Market went crazy over that release and since that time how much money has been lost by those who had to be early owners?
If you do not have a solid income stream the business isn't worth anything no matter how many members you actually have and the same applies to Apps and App Adds. You might get millions of people forced to look at them but very few actually buy. As mentioned above I don't know anyone who has parted with their money but maybe that's just because I associate with the wrong crowd.
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