Where do the miners/pools connect to get their problems to solve?
Sorry for the noobness, but I am too lazy to study the white papers.
It could be harmed if a malicious user controls more than 50% of the computation power. The decentralization exists, but I doubt that it will scale... Anyway, we have more important things to worry about right now. Here is a nice wiki reading: https://en.bitcoin.it/wiki/Weaknesses