Anyone who thinks that they shouldn't take advice from hackers should never be a lead developer on ANYTHING. Hackers provide some of the best advice you'll ever get on a project, especially if they are willing to talk to you FOR FREE. Many hackers would make you pay for the kinds of things that ArtForz told you. If a hacker tells you of a possible attack, as the lead developer, instead of ignoring them, you should LISTEN and DROP EVERYTHING to fix the issue. Not doing so results in what we just saw. It also results in things like MtGox, Mybitcoin, and Sony.

True blackhat hackers won't even reveal themselves, let alone talk to you. If someone warns you about something, you should heed that advice, regardless of who it comes from.