Tapping fusion power will solve the world's energy issues, and that is a good thing.
Is it though? Exponential growth always has to end in disaster sooner or later.
Global energy use in 2008 was estimated at 474 exajoules. At a 8% yearly growth rate in consumption, it would take only 120 years to increase that to 5 million exajoules, thereby producing more waste heat than the energy which the earth receives from the sun. It's likely that we would be in serious trouble long before that.
(If the 8% growth rate seems high, I took it from the growth rate in oil consumption before the first oil shock in the 1970s. This seemed like a reasonable model for growth in a world with limitless energy supply.)
It's actually not reasonable; since the 70s there have been significant pushes toward efficiency on a variety of fronts which make pre-1970s energy consumption statistics inapplicable.
But nothing's ever "limitless," though -- energy would still cost something (even though it could be 1/100th of what it is today). Transmission and storage of energy would still have costs and that's where the drive for efficiency would come from.
