You know whose REALLY got to be kicking themselves is Xerox! They did a lot of the R&D on GUIs in the 70's. (I even remember seeing their TV ads about GUIs on the evening news) And they ended up passing on the technology 'cause they didn't think there'd be a market for it!!!
http://www.fireinthevalley.com/
A lot of great historical information there. It documents how Steve Jobs took what Xerox accomplished, and how he built on that technology and greatly improved it - only to give it away to Bill Gates. Apple later sued Microsoft because Windows "stole" GUI concepts from Apple. True in the sense that many concepts were conceived by Apple and not Xerox. But the book shows that Steve Jobs instructed his people to give free access to Bill Gates for the Macintosh GUI software code.