so, I really don't know the details of any business relationship we have with Snap, and I have to confess the previews bug the crap out of me, too.
But here's the thing: Regular people on the web *love* Snap previews. I know you don't believe it -- I didn't want to believe it. But it's completely true. In the testing and feedback I've seen, it's some emotional pull about the fact that links "do something" now, instead of just being on the page. I know we all feel these people are idiots, but it's our own geek cultural imperialism that makes us think we know better than non-techy folks.
I can't claim to really understand why this is the case, but I know far better than to question people's emotions about such things. :) My first reaction was "ew, omg, opt-in only, please!", but you will be totally shocked how many people will delight in having them. And yep, you can block 'em completely for yourself.