Ask HN: Appropriate levels of email contact?

More and more I despise signing up for new websites, because they all seem to think the act of signing up grants them permission to spam me as much as they want. I'm not talking about sites like "Debbie's torrent house", but "normal" sites like Airbnb.com (YC09), for example, who has spammed me 3 times about rating the last place I stayed at.

I'd like to think that it's just because they're pretty new and inexperienced about customer interaction, but I know better. For some reason, some marketing schmuck (or some engineer in the role of marketeer) gets green colored eyes the moment they think about email addresses.

What will it take to teach startups that just because I sign up for your website, I am not a marketing lead for you to abuse?