A few years ago, LinkedIn asked me if I wanted to upload my address book to see which of my friends were already on LinkedIn.
It then proceeded to spam all of my contacts, pretending to be me, several times.
Because Gmail collects addresses automatically, it sent spam to ex-employers, ex-girlfriends, and clients. It was an absolute nightmare. It makes me angry thinking about it to this day.
If there's any company I wouldn't trust with your email, it's LinkedIn. Their practices are absolutely disgusting and unethical. I believe there's a class-action suit against them for this exact issue.