There is an article (Cloud computing is a trap, warns GNU founder Richard Stallman) talking about cloud computing, it points out that cloud computing will definitely lost people's privacy while people using these applications.
Now, the web applications are more and more popular, people exchange information, check email, communicate with their friends/family, and even though get entertainment on Internet. However, people lose their privacy incidentally when they doing these activities.
In my opinion, the problem may become more serious which also indicates by the last paragraph of this article. The main companies host these web services are reliable(?), for example, Google, MS, IBM...etc. However, if you use a proprietary program or unknown people's web services, you are under the dangers of losing privacy. Can regular people/users distinguish trustful server? Personal security may become a important issue in cloud computing.