im moving my desktop back to ubuntu after a few months on vista. i've been thinking about pidgin and how it works and finding out its not as extensible as i was hoping. as i was shuffling windows around so that my IM list had its own spot in the corner i thought for a moment that a second monitor would be nice. i've had a second monitor before and i find it to be information overload.
if you think about the iphone cradle, its angled to work like a second screen. you're going to want your android smartphone to have a really good IM/activitystream application anyways. so why not set it up in the cradle when you're at the desktop.
if you're getting an IM, you're going to want to use the desktop keyboard and mouse to interact with the phone app.
activity stream updates are going to be wide. as in a line of text, usually. cell phone screens are not wide. maybe the screen is too small to use as a second "dedicated IM/activitystream" monitor