Ask HN: Is it OK to invest $$$ from a profitable biz into an unrelated startup?

I just read an article where the author is being crazy transparent about his finances. He burned $1.4M and today invested another $1M. The entire $2.4M was taken from another business of his. see here: http://startuplabs.com/blog/today-im-going-to-invest-1m-into-finic-inc/ My question - Is it a good idea to invest cash from a profitable business into an unrelated startup?

I currently run a consulting business and am thinking about investing part of cash I earn into a startup idea.

If the startup is unrelated - isn't this a really bad idea?

There is a discussion here talking about building a product within a consulting business which is unrelated to the business itself, they had to shut it down because of amount of friction it caused and the focus it took away from the team: http://mixergy.com/interviews/bryan-zmijewski-zurb-interview/

Curious to hear everyones experience with this.