Is this Ethical (using email lists)?

BCC those bastards, bloggers like me does it all the time, and get personal!

It was a dumb thing for them to do. When my friends do that, I ask them not to make my email address public (which is totally avoidable).

It is hard to say how the law would look at this. It is probably a gray area. If the events you are promoting involve payment for tickets, then unless you have a business relationship with that email adressee, your mailings could be regarded as spam.

Using email adresses obtained without the accountholder’s consent for commercial purposes, is not only unethical, but illegal in many places too.
You could take your chances as long as you make sure you inform the recipient of how you obtained their contact details and offer an opt-out. Even so, unless the person who shares the addresses with you has the recipients consent to pass them on for further use, you could both get in trouble.

Technically, it’s spamming.

Most email hosts (be it from your ISP or elsewhere) have strict rules against it. That said, in the situation you’re giving, it’s nigh impossible for them to detect. But then again, if the recipients didn’t want to receive the emails, they could report it as spam which, if enough people did it, could land you on a blacklist or two – which could impact future campaigns or get you in trouble with your email host.

So I guess it’s down to your morals. I wouldn’t do it personally. Really, if you want the campaign to be effective anyway, you need to send it to people who actually want the email.

Here’s a way around your moral dilemma, which has a high probability of all those email addresses still receiving your promotions: Send your promotion email(s) to the friend who emailed you without BCCing, and include a request that your friend forward it/them to all his or her friends, and so on.

no one wants spam.
My company builds list for our marketing department but we always ask permission before sending anything out anything to anyone.

Only use it for your own promotional purposes if your goal is to totally turn people off to what you’re doing.