"Growth hack" is an industry euphemism for "unethical practice." You can tell it doesn't literally mean "growth hack" because it's being applied here to the website that Alexa currently ranks #152 worldwide and the typical excuses about how you need to get a little dirty when you're a tiny business just getting started don't remotely hold water.
Not all growth hacking is unethical. WePay's $100 bills in a big block of ice dropped off at the PayPal conference comes to mind. Or Dropbox giving you extra free quota for going through their tutorial, installing on a new device, or inviting a friend (where the friend also gets extra free quota).
I don't about the other ones, but giving you extra when you get someone else to join is unethical. MCI started this trend with their "friends and family" promotion, and it really pissed people off. People who don't use the system hate being pestered by friends and family to join something they don't want or need.
