I'm not going to use Intro, but I have to ask, how is giving LinkedIn access to my email account any worse than giving access to Google, Yahoo, or Microsoft--by virtue of using their webmail?
A secret is kept secret by sharing it only with someone you trust, and with the smallest number of people possible. Ultimately, you have to share your credentials with your email provider, because they have to authenticate you in order to gain access to the information stored on their systems. Each additional party you share your credentials with increases your attack surface.
Given the number of security disclosures -- oops, someone got our database full of passwords, but don't worry, they're MD5 hashed -- that have occurred over the last couple of years, I'd be extremely cautious of that practice.
Given the number of security disclosures -- oops, someone got our database full of passwords, but don't worry, they're MD5 hashed -- that have occurred over the last couple of years, I'd be extremely cautious of that practice.