Ways the singularity could fail to happen

[ciphergoth]

Dashing off a quick post with some half-formed thoughts just to see what people think. When I refer to the singularity here, I mean it in the intelligence explosion sense. I'm trying to categorize the different ways the singularity could fail to happen, here are the categories I've come up with so far:

• Human minds might be fundamentally different to other physical things, and not subject to thinking about like an engineer
• The idea of one mind being greatly more efficient than another might not be meaningful
• Human minds might be within a few orders of magnitude of the most efficient minds possible in principle in our Universe
• ... as above in our corner of the Universe
• ... as above given the height of our physical knowledge
• ... as above given the limitations of the height of our manufacturing ability
• ... as above given the limitations of the height of our design ability
• We might not continue to study the problem, or the relevant fields necessary
• We might hit an existential risk before reaching the heights of our potential
• We might have the ability to build superintelligent minds, but choose not to do so
• We might build superintelligent minds and it not make a great difference to the world

What have I missed out?

EDITED TO ADD 15:20: just added "The idea of one mind being greatly more efficient than another might not be meaningful", which is a popular one.