The cameras I use have the date/time stamp but I never use them as it seems to distract from the photo. If I want to know when a picture was taken I just hold cursor over photo, right click, and click on "Properties" and this will show date and time of photo taken..it probably depends on which photo software you are using though.
When we upload photos into our MLS database they automatically get a watermark so photos can't be robbed and used again in the event of an expired.