graeme_p - 12:17 pm on Aug 17, 2013 (gmt 0)
90% of users are unaware, probably true but:
1) If they are Gmail users they have not bothered to read the TOS, or read anything about Gmail, or have given any thought about how the free service is paid for.
2) If they are not Gmail users, it does back to the recipient whether the sender of an email can restrict what the recipient does with it.
In either case you must know Google does some sort of processing with it. Google does not "intercept" the concept, they are sent the content with the expectation that it will be stored on their servers.