I think even 1% or 2% can be too much for some people, but I'd say that everyone should invest as much as they can afford to lose in Bitcoin and maybe a few other coins, because the potential payoff can be huge in the long run. I think many investors have already taken this approach, but maybe they prefer to not talk about it for some reasons, like maybe they don't want to be judged by their Bitcoin-hating colleagues.
I can't see how investing 1% or 2% of what they have can be too much for some people. However poor they can be, we are talking about percentage here, right? Percentage is a proportion or share in relation to a whole, and the poorer person is, the less money he/she is investing when investing 1% or 2%. It can't be be too much for "some people", it's either too much for everyone or not too much, regardless of the financial situation of an individual.
Novogratz has invested 10% of his net worth in cryptocurrencies himself and I agree with him because if you lose 10% of what you have it's not the end of the world.
No one should risk more than they can afford to lose, but if you are afraid of risking 1% or 2% of what you have how can you live in this world?