I've only played for myself and one friend. The fact that they called us for using the same computer makes me not want to try it again with someone else. Well I might, but I won't push for the friend bonus

. Neither of us answered our phones when they called (they called us back-to-back and we were together at the time). So I called them back, once as myself and once as him (with his phone). They did ask a couple questions only the person playing the account would know, so just keep your friend up to date on what you're doing with his account-deposits, dates, withdrawals, etc.
In theory I don't think it's wrong either. You take most of the money, but maybe cut in your friend a little since he's helping. I view it as your friend selling you his rights to play for that bonus. But I think most online casinos state in their terms you're not allowed to do that.
I've never played Ace Club, but I've had quite a few downswings. My worst was on bet365 (my first actually). I started off unable to lose. Upped my bet and kept winning. Took the initial $400 up to $1100, and then gave back all but the initial deposit. Let's just say I learned my lesson. Of course that downswing was due to stupid bets.