For Bitcoins: no, the amount of miners doesn't increase the amount of Bitcoins created. It only increases the difficulty. There is an absolute maximum for existing bitcoins, around the half is created so far. but the economy connected with Bitcoin is small. At it's maximum it barely broke 2 billion dollar in size - that sounds much, but that is the value of all existing Bitcoins. At such small size it's value is easy to manipulate through speculation. The value should be 10000$ per Bitcoin or more to give the currency more stability.
The strong increase was clearly a bubble. Bitcoin should grow slow in value, that has to be connected to real stuff you can buy for the currency, that would lead to a substantial grow.







