I'm interested in using machine-learning and nlp to try and get insights into people, and key-logging allows you to capture the maximum amount of text data of a user. 

I would like to try building a data-set on my own interactions with my computer and my phone, but was wondering why I couldn't find online any examples of this sort of thing being done.

I would like to first test out the effectiveness of my dataset on learning about me, before offering for others to try out my work on themselves.

People will obviously be sceptical of a keylogger being used to gather data (passwords, banking details, etc) but is there actually anything stopping someone honest from using a keylogger to gather data safely?