Worried about uploading the human mind to robots
Note that he doesn't like the survival of the stronger
This from Cosmic Engineers:

In a future with uploads, human minds are ultra abundant. They can exert themselves anywhere,
anytime, anyplace. If that is in fact paired with material affluence (and aquiring money), the individuals
who have means will attract more means exponentially so, and displace those with less. i.e. you get
radical disparity in minutes. and it doesn't end there - those with an ultra-consolidated hold on society
will imprint their values (say, very rich uploaded wahabi, or russian gangsters, or ex dictators or fox
managers or former oil people) on society, and thee values may not be the noblest values.

Democratic systems will push back against disquality and inequality. It must push back against the
values and goals of single individuals, because society will over all not share their values. The scary
part is this won't happen in some countries, such as dubai, and the end game there looks decidedly
bleaker for those not on the winning side.

I have argued in the past that disparities of affluence and political influence will almost certainly
magnify into existential risks. I argued to the Lifeboat Foundation to include Disparity as an existential
risk, but so far the notion seems politically taboo.

The compromise (and I agree, not the ideal situation) is curtailment - laws. Society (and probably the
overarching community of nations) will step in to curtail personal manifestation. That means an AI girl
taking over the 7/11 nanofacs, and soon after Idoru crawls out of the replicators in every printer of every
store all over the world will be illegal. At some point states may declare overexertion illegal.

We are close to that point already and I am voting for it. For example, I do not condone that certain
religious minorities have active displacement strategies by having many offspring (over 5 children) and I
would push for laws outlawing parenting of more than 4 children. Yes this offends many people, and is
belittling and patronizing and very rude, but I base my preference on my insights of the severity of the

At heart I am a pandorist- I want as many people as free as possible to do as much as they can and like,
but in the real world I am a anti-displacist. I don't like nature, where everything is constantly eating
and killing other things. I suppose I am against zero sumism. I can't stand marginalization - not
because I particularly like latter-day marginalized (I personally can't stand that category of soccer
watching simpletons in my country)  but rather because I find myself marginalized and I know how
dangerous it is.

There could be other reasons, though. Can anyone think of another
reason why an upload is restricted to one machine as its substrate?