Peer to peer is an important part of 21st century advertising. Peer to peer replaces the slow, impersonal work sales people and broadcast advertising campaigns would perform in the 20th century to educate customers and to negotiate the customer's needs and budget.

Nowadays it is very easy to find people just like you online and ask them what they bought and whether or not they are happy with the product (although not everyone has trained themselves to do it).

That neighbor to neighbor information dispersion replaces a lot of the function of broadcast advertising.