Craigs List
There's a spot on TV about Craig's List - they showed Craig - the guy who started it - Craig Newmark (a nerd) He started the list as a way to make friends - and it worked! He's now on Times list of 100 most influential people. Diversity of Options, finding everything - large advertising - community - business. Although it's free - it has produced millions of dollars of commerce. Of course I heard about it first from my daughter ;-)
Homes filled with items from Craigs list - some paid for - some free.
Newmark has turned down huge sums of money to sell his list. He clocks in 7 days a week - policing it for rip offs etc. (which have happened) He's an innkeeper - it's his list & his place. (What if you take the Craig out of Craig's list?) E-bay & others are trying to be competitors.
Some people have found dates for events on the list - and later their spouse.