That's a tough one. I have had people make ethic comments if I have to explain how I got flights for free. I don't understand what's unethical about the credit card signups. Closing them after a year does hurt your average age of accounts so it's not like the credit card companies aren't aware and you are sneaking something by them. But people's perceptions are very hard to change, especially when it comes to ethics/emotions and not logic.