Using open source services means making sure that you will never be controlled by a particular website, but also that you can always migrate your data elsewhere.
Centralized services raise many problems: they make your data very vulnerable (one inaccessible website and everything is down) and make it very easy for third parties to exploit your data.
Using decentralized online services means maintaining a choice between using an online resource such as those offered by Framasoft or installing/managing the service yourself.
“If it’s free, you are the product”: many online services make a living by exploiting your personal data, i.e., selling it to advertising companies. Furthermore, most of these services are based in the United States and obey US laws like the PATRIOT ACT which deny all rights to privacy.
Using online services hosted in Europe means ensuring that you are not dependent on the laws of another continent. In addition, by hosting the service yourself, no third party can violate your privacy.
Freedom-depriving services ("proprietary" in everyday language) are totally opaque: it is impossible to know exactly what the software does with your data. Only the publisher has control over it.
Using Free online services means being sure the community has control over the software and maintains the ability to modify it, to install it elsewhere, etc.
Edward Snowden’s revelations about the PRISM program of the @:camps.nsa.title showed that fears about massive violations of users’ privacy were well-founded.
