With all of the online communication services like e-mail, social media sites we use today, pretty much all of them are "free" services in the sense that we don't pay them any subscription fee for using the service. And as such the "Terms of Service" are heavily tilted towards the service provider.
In most cases, the only way such free service provider makes money is by mining the data they collect when we use the service. Every time we use such service we are inputting some data for query, transmission or storage. Most of the time this data is sensitive, confidential, private data like your contacts, personal messages that reveal who you are, what you like or don't like, what, when and where you do things etc.
By mining this information for profiling the user and using it to show targeted ads or to do market demographics research and sell that information to marketers are most common ways of making money. In such cases, no particular user's data is specifically exposed as it's all aggregate information. So such uses may be acceptable.
But what is scary with this is unauthorized, accidental data leakage or theft of data by illegal "hackers" or even government powered agencies getting access to this data to spy on people or corporate espionage.
I don't know if there ever will be a complete solution to this problem. But, to start with we need guarantees about privacy and security from service providers. It should be verified and certified by multiple 3rdparty agencies. It should be scientifically provable. And there should be stringent consequences for breaching this guarantee irrespective of whatever the reason may be.
Now, I know such security is difficult and will cost a lot of money. So, it is acceptable to have subscription fees to cover such services.
What is alarming today is there are absolutely no such services in existence. Even if someone values their privacy and security and are willing to pay subscription fees for it, they have no choice but to use ads powered free services.