Legit Technique or a Serious Breach of Privacy?

When you sign up for many of the popular social sites, there's often a page that allows you to import your contacts from the major email accounts, like AOL, gmail, yahoo mail, etc.

There's a Warrior or two (that I like and respect) that seem to have given my email address to these services, as I consistently get invites in my email box.

There's also now a script you can install on your sites that will do the same thing. When someone enters their info into a squeeze page, they are given an opportunity to invite their friends. The "friends" are contacted using the same means, by reading the details of your email account.

It's probably a great way of marketing...But I also feel it's a great breach of privacy. I doubt I gave you permission to give my email address to LinkedIn and other similar services.

And I sure wouldn't allow anyone else to have access to your email address through my own email contacts.

Is this legit marketing and am I the only one that's concerned about this? Or do you agree this is a huge breach of privacy?