Why didn't the Romans have hot air balloons?

That is not quite entirely true, war -- especially long-term -- results in huge funds being funnelled towards things that can blow up the other guy, which can then move into more peaceful realms. Not to mention the requirements for research safety and grants are often quite different.

Without WWII, would we have operational jets in the early 40s? What about rockets? All of rocket science from the late 40s and early 50s came from WWII germany. Likewise for fission and fusion research, how much longer would it have taken without Los Alamos?

> Competition invites advancement, blowing up your competitors does nothing.

That's crappy pop-history that's largely been discredited. Inventors generally don't need motivation, only funds (of time, of money, of equipment, of relations). And the reason for those funds and where they come from is the lowest of worry, as long as they are provided. Competition is irrelevant to invention and advancement.

"The Montgolfier brothers came up with the idea while lying beside a fire and watching hot ash and embers float upwards – and they thought about this in a military context – namely how to take Gibraltar from the British."

And later

"However, Hero of Alexandria (10–70 CE) was well known for constructing complex automata, had powered a pipe organ using his wind-wheel (windmill) and developed a variety of steam driven devices using his aeolipile; a primitive turbine type steam engine with surprising motive capacity."

From wikipedia http://en.wikipedia.org/wiki/Hot_air_balloon "Unmanned hot air balloons are popular in Chinese history. Zhuge Liang of the Shu Han kingdom, in the Three Kingdoms era (220–80 AD) used airborne lanterns for military signaling."

"In fact, von Braun was engaged in designing and building the V-2, and much more sophisticated rockets, solely because he wanted to achieve the exploration of space; both personally and for the human species."

In each example above where technologies were invented / discovered, you can see that these innovations were driven by individuals and their purpose. In the case of the automata and the hot air balloon, both were invented by a leader of their own respective society - "Hero of Alexandria" and "Zhuge Liang" - the chinese military genius. Von Braun wanted to invent rockets for the purpose of space exploration... but his effort was redirected into war and destruction.

Comparing to innovations we've made in the past, say, 30 years, you can see the same. Bill Gates commoditized hardware and brought computers onto many desks cheaply. And Steve Jobs... you know the rest.

Each story of humans' invention seems to just as much be a story of the individual who led its discovery, rather than the environment surrounding him/her, and when the environment is taking into account, it seems it does more to stifle innovation than to foster it.

Also - I signed up for the service - I love the idea, but if you expect me to sign up to Facebook just to start using your service - then forget it.