About 10% of my liquid assets are in Bitcoin, if we use today's USD values.
That wasn't a deliberate decision though, I bought the coins when they were considerably cheaper. At the time it was a tiny proportion of my assets, more like the type of money I'd spend in a big weekend. I wouldn't put 10% of my assets in Bitcoin now, by any means.
I know that logically that means I should cash out the coins until I have a less risky proportion invested, but there's a psychological difference there.
However, the knowledge that I have so much in Bitcoin makes me choose my other investments more conservatively.
I've also cashed out a proportion of my original investment in the past, so no matter what happens I am still way up on Bitcoin. It's performed many times better than any other investment I have ever made. However I got seriously lucky with timing.
If for any reason I felt like it was more than I could afford to lose then I'd cash out in a heartbeat. No one, no matter how much they believe in the concept, should have more than they can afford in Bitcoin.
The people who have ridiculous proportions of their money in Bitcoin, in my opinion, are making an irrational decision. Perhaps it is greed, perhaps it is zealotry. For whatever reason, they have a confidence in Bitcoin that defies logic. Good luck to them, but it a car crash waiting to happen in my opinion. I couldn't sleep at night!