This is a real shame if true, and I lay the blame solely at the BTG developers. In ANY new cryptocurrency project it's necessary to consider the roll-out, communication and user experience not just writing code. Failure to do so results in user frustration, scams and an unsuccessful project (usually). This isn't even new information, we've seen it happen time and time again with projects that implode from lack of timely updates or not communicating with their userbase well enough.
Finally, NEVER trust your private keys to an online service ever , unless you're willing to lose them.