Now they have even more reason to fear their privacy, since Facebook is rumoured to be bringing ads to Messenger. The company hasn't confirmed the rumour, but TechCrunch has unearthed a document suggesting that Facebook will launch ads within Messenger in Q2 2016. See also: How to block Candy Crush Saga on Facebook
Can Facebook Messenger spy on you
Despite what you've heard, Facebook's Messenger app isn't going to call or message your friends or use your device's camera to see what you're up to. For one thing, Facebook would get into HUGE trouble if it did, and it wouldn't be tricky to catch Facebook in the act, particularly after all of this bad publicity highlighting such privacy issues. Also see: 13 best Facebook tips and tricks.
The app does not give Facebook "direct control over your mobile device," either, despite what The Huffington Post reported at the time.
In fact the Messenger app's permissions aren't much different from the main Facebook app that you've been using for years, and there are probably several other apps with almost identical permissions installed on your device already.
On Android, downloaders of the Messenger app have to agree to give Facebook permission to access the device's camera, microphone, contacts, location, calendar, WiFi information and more, which does seem rather daunting.
However, those permissions are the same or very similar to most other messaging apps, including WhatsApp, Snapchat and Instagram.
Plus, on Android, Google requires permissions to be worded in a particular way no matter what they're actually used for, so when you read that the app wants you to give it permission to "take pictures and video" or "directly call phone numbers" it doesn't mean that the app is going to do either of those things without your knowledge.
NOTE: Facebook Messenger has always been able to - in common with the majority of other websites, apps and online services - collect and use your data for advertising purposes. Some would consider this to be 'spying' on you, but not in the way that many reports are suggesting. (Below we'll explain what Facebook's permissions really mean.) See also: How to delete cookies and web browsing history
With regards to the rumours about ads coming to Messenger, Facebook told TechCrunch: "We don't comment on rumor or speculation. That said, our aim with Messenger is to create a high quality, engaging experience for 800 million people around the world, and that includes ensuring people do not experience unwanted messages of any type."
Facebook knows it has to play the ad card carefully, so our main concern here is how it will work out what type of messages you might want or not want to see in Messenger. We are unable to comment further until Facebook reveals - assuming it will - Messenger ads.
Read more: Tips for private browsing
Why does Facebook Messenger need access to your camera
If you want to send a photo to a friend directly through the Messenger app, you'll be asked to give permission for the app to access your camera. It's not asking you to let it access the camera so that it can watch you while you're sleeping.
Why does Facebook Messenger need access to your microphone
If you want to voice call a friend through Facebook Messenger, the app will need permission to access your microphone, because otherwise it wouldn't be able to hear what you're saying and neither would your friend. The microphone is also required for recording and sending video clips with audio.
Can Facebook Messenger call my contacts without my knowledge
You'll need to give Facebook Messenger permission to directly call phone numbers if you want to use the app, but it won't do so without your knowledge. What the permission actually does is allow you to call a Messenger contact by tapping on their phone number.
Can Facebook Messenger text my contacts without my knowledge
Facebook also requires permission to edit, receive, read and send SMS messages, which is understandably confusing, but you can rest assured that the company isn't going to send your friends messages without your permission. The app needs you to allow it to have control over messages to allow you to confirm your phone number via a confirmation code that Facebook sends to you via text message.
Giving Facebook Messenger permission to read your contacts will let you add the contacts stored on your device as Messenger contacts if you want to.
It does seem more daunting when you're asked to give these permissions on Android because you'll be shown all of the possible permissions that Facebook Messenger needs at once without an explanation of what giving those permissions to the app will enable you to achieve. It's slightly different on iOS, because you'll be asked to give these permissions one at a time when you use various features available in the app. See also: How to stop Facebook automatically playing videos
"Almost all apps need permission to run on Android, and we use these permissions to run features in the app," writes Facebook in a blog post explaining why the Messenger app requests permission to access features on Android. "Keep in mind that Android controls the way the permissions are named, and the way they're named doesn't necessarily reflect the way the Messenger app and other apps use them."
So, while it is pretty annoying that Facebook wants us all to download the Messenger app (we all hate change, but we'll get used to it), don't let scaremongers put you off of downloading and using the app. All apps come with privacy concerns of one kind or another and Facebook Messenger is no different, but it's not going to spy on you and it's not going to send messages to your friends or call your family without you knowing. See also: How to deactivate or delete your Facebook account.
If you want a bit of a giggle, you can watch the Fox 29 report that's been doing the rounds this month and scaring people into believing that Facebook is going to spy on you. While some of what he says is true (Facebook, as well as the rest of the internet, is collecting data from you in order to show you adverts it thinks you will be interested in), you shouldn't believe everything he says.
After all, Anthony Mongeluzo, who is apparently a "tech expert," calls Nike's FuelBand the Nike FitBand and also suggests that WhatsApp is called What's Up App.
If you are still concerned about privacy, you can follow the links below to find out more about how to protect yourself and others.
How to share a PC or laptop and keep your data safe
What is Cartoon HD and is it safe
How to stay safe on social networks
Top 6 security tips to keep your smartphone - and your data - safe