Who's sharing data

Al has a post asking what people would do if their information was shared after opting out of any sharing.
It’s a tough call and one I think about as I see mail coming to my mailbox to such addresses as laura-sony and laura-quicken and laura-datran. All of these were addresses given to specific companies and where I attempted to opt-out of them sharing my data with other companies. Somewhere along the line, though, the addresses leaked and got into the hands of spammers.
Those addresses are overwhelmed with spams and scams. The frustrating part is there is no way to fix it. Once the addresses are leaked, they’re leaked. They will be receiving spam throughout eternity, even if the companies involved stop selling data or fix their data handling problem.
I don’t know what to do, honestly. If I think it was a one time thing, such as the addresses that started getting spam after the iContact data leak, then I’ll change my address at the vendor and retire the address the spammers have. But with other vendors, I don’t know what happened and I suspect the vendor doesn’t either, and so I can either deal with the spam or hope that I don’t lose real mail from that vendor.
There’s no easy answer. Any time you hand over an email address, or any other form of personal data, you’re trusting in the company, all of their employees and all of their vendors and partners to be honest and competent. This is often not the case.
What do you do?