Earlier quoted context omitted.
The danger I see with UBI, is (in addition to possible inflation, etc.) is that commentators on HN tend to be of higher education, curious, and simply "hackers". Most people here would love to be payed money so they could sit and program some cool OSS, start a new company or simply change the world. For them, UBI is fantastic. How many more Googles/GNUs/Apples would there be if engineers could quit existing companies…
The problem you point to is self-limiting. Regardless of the nominal level of UBI, it won't provide a satisfactory income unless a sufficient number of people remain working to provide the goods and services required to provide a satisfying style of life for the UBI-only recipients and sufficient additional value to workers for them to continue working. Prices will adjust to make this the case. As the quality of life…
My biggest concern with the UBI is that looking back at societies with UBI (such as the upper class Europe of the Middle Ages through the 19th century), for every Newton or Voltaire were many more unknown nobles who spent their life grooming their mustaches.
I don't believe our society is that much better now.