Or alternatively (and in my mind, more likely), the massive gains coming directly from computer technology has reached its peak. There will never be another new purely "technology" (i.e. where the business is primarily built-on computer software, internet, and/or hardware) company that's as profitable and powerful as Google or FaceBook

There will always be scope for solid good new businesses with big and small margins, but maybe the next FB / Google will be in some other field? Maybe biology or nutrition, maybe quantum physics, who knows. I wish I had some ideas though.