Prefiguring Cyberculture: An Intellectual History
ed. Alessio Cavallaro, Annemarie Jonson, Darren Tofts editors
MIT Press,  October 1, 2004.  
Damien Broderick, Racing toward the spike, pp. 278-293

Once personality uploading is shown to be possible and tolerable or, 
better still, enjoyable, we can expect at least some people to copy 
themselves into cyberspace.  How rapidly this new world is colonized 
will depend on how expensive it is to port somebody there, and to 
sustain them.  Computer storage and run-time should be far cheaper by 
then, of course, but still not entirely free.  As economist Robin 
Hanson has argued, the problem is amenable to traditional economic 
analysis.  "I see very little chance that cheap, fast upload copying 
technology would not be used to cheaply create so many copies that the 
typical copy would have an income near 'subsistence' level."  On the 
other hand, "If you so choose to limit your copying, you might turn an 
initial nest egg into fabulous wealth, making your few descendants 
very rich and able to afford lots of memory."

If an explosion of uploads is due to occur quite quickly after the 
technology emerges, early adopters would gobble up most of the 
available computing resources.  But this assumes that uploaded 
personalities would retain the same apparent continuity we fleshly 
humans prize.  Being binary code, after all (however complicated), 
such people might find it easier to alter themselves - to rewrite 
their source code, so to speak - and to link themselves directly to 
other uploaded people, and AIs if there are any around.  This looks 
like a recipe for a Spike to me.  How soon?  It depends.  IF true 
AI-level machines are needed, and perhaps medical nanotechnology to 
perform neuron-by-neuron synapse-by synapse brain scanning, we'll wait 
until both technologies are out of beta-testing and fairly stable.  
That would be 2040 or 2050, I'd guesstimate.