There are two primary types of ads

1) ones that give you what you want

2) ones that drive demand

Google dominates (1) and I assume Facebook is trying to dominate (2) which includes a lot more display advertising (and TV, and billboards). Facebook probably thinks a lot of demand-driving advertising can be accomplished through viral online marketing through FB platforms and they are likely trying to exploit these channels with services for paying customers.

Imagine paying Facebook to simulate something being trendy among people's trend-setting friends. It'll be a fine line but this must be what they hope to do.

Agree the $100B is too high, but certainly they're easily a profitable company, long-term.