Here is an interesting app that is very useful for collecting contacts
https://itunes.apple.com/us/app/yun/id1000536929?mt=8
http://yun.yproduction.com
Users can simply leave this app in the background.
It will keep a link of every other users they met in the location automatically.
Then one can click on a Like button on specific users to show interest.
If both party "Liked" each other, they will be able to connect and chat inside the app.
It provides a cool and automatic way for exchanging contacts, without the need of exposing any personal information.
CHAT