While the GNOME desktop plods on with more evolutionary than revolutionary changes, the video I just watched: Social Desktop Starts to Arrive shows that KDE isn't standing still either. They have created a social "engine" which gives user space applications (IE: applets) access to all sorts of interesting social website information. Friends, locations, etc. The big win here is that because the information is extracted out of the browser and into it's own standalone engine, suddenly all parts of the desktop will have access to (theoretically anyway) your facebook, twitter, myspace, etc data.
Yes this can be done now, and it's not like there aren't twitter clients for the Linux desktop, but in a very KDE move they have made a single data engine for this so the wheel doesn't have to be re-invented all the time, and applet/app developers can move faster to get cooler programs out to the world. Check out the video anyway, it's a nice demonstration of what those rascally KDE guys are up to!