This will always depend on the level of skills and understanding a user has about Linux in general and Ubuntu.
Like everything in computers doing stuff around were you have no idea what is going to happen is never a good choice. It can happen with Linux, Windows, Mac OS and all the rest.
The thing is most people will see all packages that run in Ubuntu as something that is part of Ubuntu and should be Ubuntu's responsibility to support them and fix everything related to then in case something happens.
At the same time if a Windows user crashes a system because he remembered to install some random software that clean up his registry, he will probably blame the software he installed. This is just an example.
Ubuntu tests in Alpha and Beta stages of a release for problems with packages, it is not in anyways responsible to what happens to your system by using them. The same goes for guides and random commands you see in the Internet. If you do not know what you are doing or what a package will do to your system the best choice will be not to use them.
A clear case of that is CCSM, normally people will recommend it every time someone asks Is there a way of customizing X in Compiz.
CCSM is great! But a very elaborate and complex tool because Compiz is elaborate and complex. People need to realize that using it can break your system if you do not know what you are doing. People still want to use it to customize X and Y, but that is their choice. You cannot blame Ubuntu for what you do to your system using it.
Unless you know what you are doing or you know how to revert back I would stay away from anything that involves:
- Random PPAs with improved versions or bleeding edge versions for your system;
- Random packages that promise automation of of cleaning and managing packages;
- Customization software that is proven to be unstable or has a red tag on it saying This might break stuff up!;
- Random commands that promise to turn your computer in to a super dupper Unicorn powered system, which you don't understand or you have no idea how to revert them in case something goes kapot.
Make sure you learn your system and make sure that what you are using is really required, most of the times it will prove not to be the case. In the end it up to the user, low are the cases were a actual package breaks stuff around just because it is installed.