Cloud computing is the idea that you can store and/or process information on another computer using an Internet connection. While this is typically done for convenience sake, it has many issues associated with this structure of computing. The name 'Cloud computing' is a little misleading, it is designed to hide the fact that these tasks are handled by using a computer that is controlled by someone else other than the direct user. When ever you see the term "cloud" in relating to computers, think "someone else's computer".
Examples of these (dis) services' are Google Docs, Microsoft OneDrive and Apple Music. These are just a few of many thousands of similar products but all of them have the same problems. That when these tasks are can be done locally are provided by someone else externally then they are the ones in control - not the users.
When you store any private data in an online service, there is no guarantee that your information and data is secure against other people looking at it or anything stopping them sharing it with others you do not want such as governments, companies and other malicious players. As much as they can talk about security there is no way for you or anyone you trust to personally verify their claims. This is a major breach of privacy as it means that your personal information can be collected and cataloged without your permission. That systems like this are required in a school or work setting should never be a thing. To force people to give up their privacy in order to get an education or a job is immoral.
A lot of these services use a term called 'Software as a Service' or 'SaaS' for short. This is where a program is loaded and executed in your web browser so that you can use a program that is provided and controlled by the ones owning the server. While these are not inherently non-free software, the overall vast majority of them are proprietary. This is related to the issues of Java script in that just because the program is more transparent to the user doesn't mean that it is not mistreating you. These programs can emulation a wide variety of programs that you would typically use on your computer outside of a browser but with the issue of additional control over your use of them. These can be document editors, graphics editors, music players and many additional functions.
All these functions can be performed locally using your computer hardware and do not require an external server to provide the program and data every time you need it. For instance, if the serve goes away so does the program and data leaving you stranded. Also, because the program is loaded from the server every time you need it and the licenses typically do not allow you to use them as you wish; they actively take away your ability to study, share, modify and share the modified versions. Even if you had the ability to study these programs one time, that doesn't mean you will get the exact same program the next time you load it. Unless you can get the four essential freedoms, you do not have free software and are being mistreated.
In the case of video and audio streaming, this has a few issues. Almost always these sites use DRM (Digital Rights Management) to prevent people from making copies of the content they are viewing. While this is done to protect copyright for the content holders it is done by using non-free software. In trying to hold on to their rights they force you to lose yours. While issues of creative works copyrights is outside of the realm of software - we believe that using a free content license such as Creative Commons is a good way to treat people in regards to your works. However, if the creator does not want to do this then that is their choice. The issue is that to choosing non-free software for works just so that they can enforce these licenses is a needless restriction. Stealing art works is illegal whether they use free software or not. It is better for the artist to not make it available digitally than to entrap people just to use the distribution platform of the Internet.
Another issue with streaming content is that even if the software was made free software and the content still has to come from an external source - there is the risk that the users will lose access to these works when the people running the server either lose the rights to the content or decide not to run the server any more.
You are never truly in control of the information these services provide.
It is best to avoid using these services as they do not respect your freedoms and actively work against you and your data. By choosing locally controlled free software system then you will be kept in control regardless of what others my wish to do.