Underlying to all of this is the idea to put more demands on the sender (there are things to pick from a drop-down and people can create multiple-choice emails, which allows the receiver to answer with one click). However, what we found is that it can also make it easier for people to write Dan because it actually removes some demands from them: they know that he doesn't expect any formalities and the structure helps them too. And, above all, senders are more likely to get a response (and quicker).
Please have a look:
http://shortwhale.com
As an example, here's Dan's Shortwhale page (he links to it from his website and in his email signature):
http://shortwhale.com/danariely
HN, we'd love to hear what you think.
Many thanks, Dan Ariely and Dominik Grolimund
PS: If you're interested, Lifehacker published an interview with Dan where he talks about "how he works": lifehacker.com/im-dan-ariely-author-and-professor-and-this-is-how-i-1615748781