This was super fun to make - hope you enjoy :) Literally a couple minutes after we posted it on fb - one of our friends commented that he worked in the building literally right behind us (I see you Minqi :)!
1. We wanted to keep it simple (1 login vs 2)
2. We thought that in general people care more about their facebook friends than their linkedin friends (contacts?) so we chose fb instead of linkedin.
3. LinkedIn also locked down their api so you can't get contacts unless they are also on the app.
Ah yeah we didn't add a link for that because we wanted people to put their real companies (and not see them and change it). You can set your company here: therealsfmap.com/company
That was our first thought as well!! Unfortunately FB no longer allows you to fetch the full friends list - you can only get a list of friends who have also authorized the app.
Re: scraping location info, we thought it'd be best to let people put in their workplace since the information on FB is typically out of date, missing, or difficult to structure. It's worked really well - the list of companies is really clean right now!