Who is keen on this? People with a fast and moving psyche, unpredictable and unstable. They are alive and bright - they never get bored with them. They also have a good sense of humor, are curious, are interested in everything at once.
The most popular current hobby is computer. This can be the maintenance of your own blog or website, and programming, and web-surfing.
Who is keen on this? People with a philosophical mindset and a rich inner world, which while quite indifferent to the outside world. Very often they try to hide from reality in the depths of their own subconscious with the help of a hobby.
Almost forgotten infatuation is science. Chemistry, physics, astronomy, biology or archeology are all those academic disciplines that have left somebody indifferent from school, and some from the institute.