1 It encourages inappropriate behaviour
Studies have shown that people tend to take more risks when they know they are anonymous or when they believe their images will be deleted such as the case with Snapchat. This can encourage people to send inappropriate photos of themselves.
2 Your photos can still be exposed
Even though Snapchat sends notifications about captured screenshots, there are still methods and third party apps that can help people take screenshots without actually notifying you. This can result in serious privacyproblems.
3 Getting blackmailed
If you have sent inappropriate photos then the possibility of getting blackmailed because of them is still present. Some people blackmail others after saving some of the inappropriate pictures they sent.
4 Getting exposed to inappropriate content
Even if you don't send anything wrong through Snapchat you are still very likely to come across inappropriate content as other people might be encouraged to send such pictures knowing that they will disappear.
5 Can easily get you attached to someone
One of Snapchat's features is allowing people to send something to others without letting them know whether this thing was only intended for them or for others as well. People can get confused about the intentions of the sender and might even get attached to someone thinking that they like them.
6 Encourages sexting
Snapchat may encourage sexting as its users will usually feel safe about sending whatever they want. Some people believe that the App was actually created for that purpose.
7 Your privacy is not guranteed
The company replied to privacy concerns saying the following, 'Although we attempt to delete image data as soon as possible after the message is transmitted, we cannot guarantee that the message contents will be deleted in every case.' They were referring to the ability of taking screenshots. (See Why Do People Care About Online Privacy?)
8 Deleted images might be retrieved
According to some experts, there are ways to retrieve the messages that were deleted. In addition to that, the fact that the images reside on Snapchat's servers for some time can lead to a privacy breach if those servers are hacked.
9 You can't really see what your kids do
If you are a parent and you encourage your kids to use Snapchat then you might have a hard time knowing what they do with the app, as images sent using the app are usually deleted from the sender's phone.
10 A playground for perverts
Many perverts and pedophiles use Snapchat in order to create friendships with teens then lure them into sexual talks. (See 13 Reasons Instagram is bad for your Mental Health)