Pinterest is totally addictive...I know this because I have fallen into the parallel universe that is Pinterest.
You can literally lose days of your life on this site.
It allows you to search out those things that fascinate you and grab your instant attention.
It allows you to have the largest space for mind mapping, without having to dedicate a wall, a room, or indeed your whole house.
You can see what makes other people tick.
Other people can see what makes you tick.
It gives you new ideas and shows you what is 'out there'.
It is endlessly updateable.
It makes you realise what is important to you.
It also lets you dream.
And that is what appeals.
(but remember that occasionally you need to come back to the real world).