What are advantages and disadvantages of low difficulty? What would happen, if it were low? and high! Can you give me some examples and tell me why ethereum developers picked 17,179,869,184 for difficulty?
The difficulty of the ethereum puzzle was not picked by the developers. It is automatically adjusted by the protocol in order to keep the time between blocks in a certain time interval.
If the hashrate of the network grows because more miners join and the dificulty is constant, then the puzzle will be solved faster and the block time would decrease. In order to maintain the time between blocks, the difficulty is raised. The opposite happens when the network hashrate decreases.
The reason why the time between blocks was chosen at its value,somewhere between 10 and 19 seconds, was to make sure all transactions are propagated properly and to reduce the number of orphan blocks.