Questions on Google lawsuit post

A couple questions in the previous discussion thread about the Google privacy case. Both concern permission granted to Google to scan emails.
Google’s stance about this is fairly simple.
Gmail users give explicit permission for their mail to be scanned.
People who send mail to Gmail users give implicit permission for their mail to be scanned.
The plaintiff’s lawyers are alleging that some subset of gmail users – specifically those at Universities that use Google apps and ISP customers like CableOne – did not give explicit permission for their mail to be scanned by Google. They’re also arguing no senders give permission.
In addition to the lack of permission, the plaintiffs lawyers are arguing that Google’s behaviour is in violation of Google’s own policies.
Google thinks scanning is part of the ordinary course of business and they’re doing nothing wrong.
This is an interesting case. I think anyone who knows about email understands that the people who run the mail server have the ability to read anything that goes through. But a lot of us trust that most postmaster and admin types consider it unprofessional to look at mail without a decent reason. There are good reasons an admin might need to go into a mail spool.
Automated filtering is simply a part of life on the internet these days. Mails have to be scanned for viruses, spam and, yes, they are scanned for targeted advertising. I’m not convinced Google is outside the norm when they say that any emails sent through Google is personal information given too Google and therefore Google can use that information in accordance with their policies.