Privacy
Email- Is yahoo messenger really private?
Yes… and no. Yahoo Messenger is intended to let you to engage in private conversations. However, this doesn't 100% guarantee that your conversation will never be available to others.

• A example of this is that the messages that you are sending can be copied and pasted there for it can reach anyone. So someone that is messaging his/her relative has no assurance that what he said can be altered and rephrased. 
• Yahoo also can remember your ID, so if you agree to those terms the site can automatically put your info in the site and log you in. So anyone can just search yahoo and your information might pop up, and he is just one click away from all your messages.
• .In addition, it is possible, although rare, for someone to capture your Yahoo Messenger log in name and password information as they pass through your organisation's network or as they cross the Internet.And you always have the people that hack into peoples account so your security and privacy can be broken into.

Facebook- With millions of users, how safe can your information be?

Facebook is far from being private because the app is for sharing information that could be showed to the public. And the privacy is very limited because you are constantly updating something ,(weather it is pictures, status, comments, etc).

• One example of this is the app they created. Essentially, by using these apps, just reading an article, listening to a song, or watching a video, you're sending information to Facebook which can then be automatically shared with your friends or added to your profile, and Facebook doesn't ask for your permission to do it. Winer's solution is to simply log out of Facebook when you're not using it, and avoid clicking Like buttons and tying other services on the web to your Facebook account if you can help it, and he urges Facebook to make its cookies expire, which they currently do not.
• The setting that Facebook uses are only to block your profile from people that you don't have as a friend. But like everything there is things that can go around that, for example if you add them "Just because" then they have all the access that they need. Because they can see the pictures that you have taken as well as scroll all the way down and see what you posted a long time ago. and all the privacy goes out the window when y'all two are friends.

Snapchat app- share pictures with everyone, how private can that be ?
Snap Chat settled with the Federal Trade Commission earlier this month over a complaint that its privacy claims were misleading, as reported by USA Today, and last week, the Electronic Frontier Foundation published a report listing the company as the least privacy-friendly tech outfit it reviewed, including Comcast, Facebook, and Google. Last year, WhatsApp faced privacy complaints from the Canadian and Dutch governments, and like Snap chat, its security has been an issue as well.

• The statement made here is that, censorship for this app can not be private because there is something out there that will break into it. There for the things you post can be copied or "screenshot-ed" and now the individual has power over the pic, something you cannot take back.
• And with this app ""snap chat or what" the firewalls that prevent the hackers from getting your information are so weak that they can easily be encrypted and broken into.

Tweeter- Even the direct message is not as private as you think.
Every 140-character nugget of wisdom you tweet will be fed to anyone who follows your Twitter account, and is also publicly searchable by default. So, if you tweet "Getting sushi for lunch today, who's in?" your Twitter followers will instantly see the message in their Twitter feed, and anyone else that searches based on keywords like "sushi" or "lunch" might also uncover your tweet.

• This is one the least private apps you can get because all you post is what you are doing or thinking. someone might not know where you live because you don't post pics, but they contently will know when ever you invite the whole world to go eat with you. And someone might not be looking for your specific tweet, but a random search will tell them and you can have someone that is uninvited to you're event.
• Another negative factor to this is that this specific app lets everyone know (not just the people following you) what you posted if they really want to know they could find out.  and you cannot do anything about this because the whole point of this app is to have messages in the internet so everyone can see.
• For example , a famous singer (byoncee) you can follow her and you will know everything she post but once she post something that she wants to get back it is impossible when you hit the point of no return.

My opinion on this that the best app would be tweeter because no one can see pic and know where you live. Al you do in the app is post things that you are thinking about. So safety is best option. And out of all this this one has the most security features on it. its been out later then facebook and has a better firewall.