Who actually makes the decisions about bitcoins anyway?
no one, and that was kind of the main design goal. There IS no single authoritarian entity.
Who decided how many and when to make generating them harder?
The original designer, IIRC an anonymous Japanese mathematician/cryptographer.
Who will decide to make more available to combat the amount that are lost?
I don't think bitcoins are really "lost". They can be stolen in a way similar that cash can be stolen from your wallet, but rarely will it be lost for good. Most uncirculated coins are just being hoarded by miners.
Supply will never be an issues because coins can be split down to 8 decimal places. That means there is a hard limit of 2,100,000,000,000,000 individual pieces of currency.