I am on KDE4 & don't see it. Are you using another DE? Maybe it isn't default on all DE.
At any rate I'll check out it's features. tx
It should be there if you have any of the 2010 KDE releases (maybe any other DEs, too).
It is not active until you run it the first time and sign up for an account. Look in the "Internet" sub-menu.
But, in any event, it's in the repos...
You may want to check out their web site: https://www.dropbox.com/