However, I don't think that exchanging business cards implies one's willingness to be put on a mailing list. What it says – at least to me – is that you're willing to give the recipient a way to contact you personally. Not, at least in the beginning, to market to you, especially if you've just met them. It doesn't take any great understanding of etiquette, business or otherwise, to treat others as you would like to be be treated.

Also, while I think in theory it's a good idea to tell people what kinds of communication you do/don't want from them, it's a little tough to put that into practice and not come off as a jerk, especially if you're meeting someone for the first time.

But unless they ask for permission, I don't expect or want to be put on an e-blast list.

However, if a brick-n-mortar business uses the old “fish bowl” approach (to enter a store raffle like a free lunch), then I expect that they will put me on an email list. If I don't like the business enough to receive emails from them, then I don't drop a card.

You are so correct. Getting permission is so important when marketing online. I get annoyed. Just because we've spoken at (insert location/event), it doesn't give them a right to “spam” me with their emails, tweets, or snail mail selling me their wares. And often, it is a product I have no use for. That isn't a way to build a meaningful relationship with me. Don't sell, build relationships.

While the recipient of a business card would be practicing wonderful businesss etiquette to ask for your permission, the fact that a business card that probably had a mailing address, phone number, email address and maybe even a Twitter name was voluntarily handed over during an event with a business context could reasonably imply permission.

Would you have been upset if they snail-mailed your something? Would you have rolled your eyes if they had phoned you? Would you have Blocked them if they started following you on Twitter?

Obviously the seemingly swift appearance of unwanted, impersonal email makes you feel like you've fallen into a trap that will never end, but here are some tips that will help mitigate this situation:

1. Don't hand out business cards to anybody just for the sake of handing out business cards; this will eliminate the need for any of the other tips below.

2. Keep a set of “personal calling cards” for social contacts with limited contact information

3. If they're using an ESP like ExactTarget or Constant Contact, click the “unsubscribe” button/link at the bottom of the email. It's not that hard.

4. Before handing over a business card to someone who you would never buy from or have need for their solution, grab a pen, cross out the email and say you're swamped with emails or your spam filter is very tight, so that's not a good way to get through to you.

5. Tell them while you would never have a reason to buy from them, you will keep their card and pass it along to someone who has and you would hope they would do the same for you. – and more direct…

6. Tell them up front please don't email you anything and to call you first. Perhaps you can say you'd love to refer people to them but you personally don't need their products/services. If they have a legitimate reason, hopefully they would remember that. If they do email you, you can contact them and remind them of your request and put them on the spot.