How do I unsign-up for this website (see details)?

A few days ago I got an email from a friend (someone who has never sent me anything even as spammy as a forward) inviting me to join a social shopping network called shoppybag . com. It went to my inbox, not my junk folder. So I clicked on the link and signed up to check it out. Before I knew it, I was getting emails from everyone in my gmail contacts asking me what shoppybag is. The same legit-looking email I got from my friend was sent to friends, relatives, even professors. OY.

I emailed a bunch of people and told them to please, please, please ignore it. And I’m hearing from people that the damn website keeps re-sending them.

I’m sure it’s my fault and there was some kind of small print I missed. I’ve looked at the site for some kind of cancel out option, but I can’t find any and I don’t want to keep signing in in case that sends more spam.

So, I know this isn’t the most pressing issue in the world, but how the hell do I get this to stop? Anyone?