it's certainly true the more people use bitcoins the better it will do. but it doesn't have to be giving it to causes (but it certainly could be). buying anything helps establish it as a money (i.e. the most used medium of exchange/store of value/unit of account in an economy).

anyone who is willing to risk and invest has the opportunity to make a profit. or if they malinvest, a lose. really it's up to each person to decide how much risk they are willing to take. personally, i like the risk, if the potential reward is there.