I'm not sure I follow your point. Of course technologies mature and opportunities dry up. The people that do technology (e.g. us here?) need to move on for gree

I'm not sure I follow your point. Of course technologies mature and opportunities dry up. The people that do technology (e.g. us here?) need to move on for greener pastures. Audio had a lot of problems to solve as digital signal processing rolled out... 20 years ago. Now, it seems very hard to come up with a product that can make good margins. An alternative would be a field like computer security, where people throw money at you do to stuff you learned as an undergrad in college. Seems like this is the same calculation everyone needs to make when planning or evaluating startup ideas. I'm always curious to hear about the current unsolved technology areas are (other than poorly-defined concepts "data science" and "A.I", that is).