Big ideas often fail for weird reasons. Take covering North Africa with solar cells and shipping the power to Europe and other places. Assuming the solar cells are on the order of 10% efficient (well within current technology), you are removing 10% of the total solar heat load on North Africa and shipping it somewhere else. So North Africa will cool, and presumeably become a more desireable and productive place to live. And thence usurp the space used for solar cells.
Same sort of thing has occurred in Southern California, which was once an agricultural breadbasket for the US, and in some cases the world. Orange county once was the source of much of the citrus in the country. But after the water infrastructure was in place to support this, it was also a desirable place to live, and now most of the citrus has been covered by houses. Same story in Walnut, California, named after local product that once was a signifanct portion of the world output.