Apple has blocked apps for a lot less than providing a feature that intercepts users' email and email password to circumvent Apple's own sandboxing and inject content into their mailbox...
Apple could yank the certificate that LinkedIn is using for configuration profiles, which would make installation significantly more difficult for the average user.
Uhm... Apple doesn't whitelist nor blacklist services -- read: TCP connections to whoever you want. LinkedIn, in this case, is well within Apple's TOS/EULA.
I think you're confused about the policies on their app store.
