Any system has its downsides, but it's the question the 'negative' effect you mentioned is a commonly heard one. However, it's the big question if this is a downside at all. With fewer jobs and more peeps around in the next few decades, maybe it is just for the best some to more peeps do not get the 'drive' to be ambitious and 'want' a paid job.
I am pretty sure, most peeps stop to do anything and contribute to society in their own ways. Take for instance my country, about 17M citizens from zero to 100+ with around 7M of them doing some sort of 'community' work by volunteering. Many of them are next to their paying jobs, but also a substantial amount by peeps without paying jobs. A good example of how many (most?) peeps are not only good-intentioned but also show such behaviour.
Don't you think AI will reach levels it can act like a human without the human realising it is AI? Singularity is not too far out in the future. This is when AI is as intelligent as humans. What happens after that, one can only guess.
