Quoting from the article:
On my desktop I use Xubuntu 12.04, and today i noticed that this distribution shipped by default the Zeitgeist daemon, a thing that I’m not using at all, for what i know.
Zeitgeist is a service which logs the users’s activities and events, anywhere from files opened to websites visited and conversations. It makes this information readily available for other applications to use in form of timelines and statistics. It is able to establish relationships between items based on similarity and usage patterns by applying data association algorithms such as “Winepi” and “A Priori”
Zeitgeist is the main engine and logic behind GNOME Activity Journal which is currently seen to become one of the main means of viewing and managing activities in GNOME version 3.0
Personally i don’t use any tool that use the Zeitgeist Framework and I’d prefer to open a terminal and use locate or find to search for files than having something that log all my activity and so slow down my system, so I’ve decided to remove this daemon totally from my system, please note that if you use Gnome 3 or Unity you could have some side effect, or perhaps the system will just become more faster, like the author of the article: Removing Zeitgeist Sped Up Unity .
Just remember that the information collected by Zeitgeist are stored for use in various forms in Unity: showing what were the last application you used, what are the applications you use most, which are the files that were used lately, the music you listen, among many other aspects. If you think you can live without these information probably your system will gain a good sped up.
The remainder of the article at Linuxaria gives provides the actual removal instructions.