I guess you cannot stop people from copying information, and that's probably the challenge for any service. They cannot guarantee the content will disappear.
The Federal Trade Commission on Thursday said Snapchat had agreed to settle charges that the company was deceiving users about the ephemeral nature of the photos and video messages sent through its service.
In marketing the service, Snapchat has said that its messages “disappear forever.” But in its complaint, the commission said the messages, often called snaps, can be saved in several ways. The commission said that users can save a message by using a third-party app, for example, or employ simple workarounds that allow users to take a screenshot of messages without detection.Snapchat Settles With FTC Over Consumer Deception Of Message Brevity [nytimes.com]
Under the terms of the settlement, Snapchat will be prohibited from misrepresenting how it maintains the privacy and confidentially of user information. The company will also be required to start a wide-ranging privacy program that will be independently monitored for 20 years. Fines could ensue if the company does not comply with the agreement.
Most of the newer, privacy focused apps like surespot, Wickr, TextSecure, and even the insecure Telegram do a better job with this. Anyone with a digital camera can bypass the "ephemeral" nature of any of these apps. Some just do a better job of making it difficult to thwart their protections in the app itself. This case should be a wake-up call to anyone who trusts Snapchat to protect their privacy in any way.