Nokia's N800 Internet Tablet has been many things, but it's not normally a platform for running VMware. Just because nobody does, though, it doesn't mean they couldn't: at the VMworld Europe 2009 expo, the N800 was demonstrated running Google's Android platform in VMware.
Video demo after the cut
That allows you to run concurrent operating systems - which could be the same or different - on the same device, keeping not only personal and business contacts, calendars and calls separate, but even different browsers, IM clients and other software. The N800 has a 320MHz ARM CPU and 256MB of flash storage; each VM only occupies around 40MB, leaving plenty of space for data files.
You probably wouldn't want to run a desktop OS on the N800, but the possibility of having a few mobile platforms on there is tempting. That way you could keep Windows Mobile, say, for its enterprise and Exchange compatibility, together with Android for its more consumer-friendly functionality.
[tip o' the hat to s_constantine]