iEventMeter is an excellent tool for gathering names and email addresses from visitors at an event. The gathered email addresses allow you to target a specific group people with common interests. E.g. you can send out surveys to them or send them commercial offers.
The collected data is transferred through mail in a CSV format. Compared to collecting email addresses using paper, the advantage is that all information is ready for use in a digital format. Also, this approach is time effective and eliminates errors due to readability and typos when copying the data from paper.
To increase the ease of use, a list of common email providers can be set up in in the settings menu.