What, in your opinion, is the difference in decentralized/distributed (client/server) architecture and centralized (Cloud Computing or Mainframe) architecture?

Q1: What, in your opinion, is the difference in decentralized/distributed (client/server) architecture and centralized (Cloud Computing or Mainframe) architecture? Give an example of a business decision that would be affected by the choice of architecture
Q2: What do you think will be the impact of Cloud Computing (or SaaS) on business in the next few years? Will BYOD be an issue?
Q3: Do you think IT Security Decision Framework can help company in providing close to 100% security? Is it used in your company?