Rekall as a Service:
The doctors at Rekall are able to detect that Quaid’s memory has been tampered with. In order to silence him, they erase his memory of the visit and send him home. This is a violation of Quaid’s privacy because the Rekall Doctors looked at Quaid’s memories without Quaid’s permission. This assumes that the waiver Quaid would have signed for the procedure only allowed the doctors to add memories and dreams to Quaid’s mind and not read the its contents.
The fact the Rekall doctors were able to detect anomalies in Quaid’s mind and send him home without remembering his visit means the technology to read and write to someone’s mind exists in this world. People could break into other people’s minds, read personal information, then remove the memory the victim has of the event. This could be done without the victim’s consent and without the victim knowing about the invasion.
Ads on the Subway:
The subway in this world have television monitors every two seats, with every monitor playing the same advertisement. Real world subways typically only have ads in the form of posters. With posters, people can opt out of the advertisement by looking away. With the subways in the movie, people cannot opt out of the advertisement because the advertisement continues even when people look away from the screen. This is because of the advertisement’s audio that cannot be muted. The privacy of people’s state of mind can be invaded while riding the subway because the passengers are subject to advertisements that cannot be avoided.