web hosting - can be in the USA but no CP/warez or adult(depending on the hosts TOS)
Can be profitable but you MUST calculate out the plans and the profit/loss margins before hand or you may lose out fairly quick. I would say have at least 2-4 months saved up for hosting incase it doesn't pay for itself right away
radio streaming - you need unlimited bandwith or a VERY high amount 1gb can easily be ran through in an hour or so without even thinking about it because streaming itself takes bandwith then each person watching eats more bandwith
torrents - you NEED offshore dedicated server or at least a VPS. I would say China, Russia, Netherlands, Germany(maybe).
cloud computing - i am unsure of, I don't want to give you wrongful information. But the above 3 I gave what information I know.
Hopefully this helps you in your decisions.