I definitely registered a domain for the simple fact that “io” meant that it was “input/output”. I am a web dev and I’m always coming up with new ideas and things that I want the world to be able to enjoy as much as I do, not just a “blog”, but an actual application.
I came up with http://mypost.io/, which is a quick, user-friendly single webpage creation platform without having to deal with hosting or registration.
It is my first .io domain and although I probably would’ve preferred a .com, the appeal of having a two letter extension was very appealing. It just makes more sense for what it does. “Input” your content. Once you input, the website will “output” your content. This is definitely what I am seeing among many io domains who might be considered “startups”, but many of these websites require the user to input something and the website will then output something for them.
I think the hardest part about io domains is the fact that .com will always register as the more primary domain and search engines are likely to list that above all else. Fortunately, the more popular your IO domain is and in demand it may be, the higher your chances are ranking right up top.