I think k8to and khim end up underlining the original point - "Embedded" is not useful word, it means different things to different people. I would subscribe closer with k8to's definition. A computer system (hw +sw) becomes "embedded" when something else than the computer system is the important bit.
Better use more clear terms:
General purpose / singe purpose system
High performance / limited performance system
Wall powered / Battery powered (power managment critical)
Qwerty and mouse / Limited input options
Big screen / small or no screen
Generic hardware / Tailored hardware
Traditionally all of the "right side" have been lumped together as "embedded" systems, but in reality most systems are mix of features from both sides.
Consider Juniper routers which have x86 and FreeBSD but the really important stuff is the custom routing hw attached to the system. High performance single purpose machine with couple of leds and buttons.
Alternatively a Android tablet built on tegra2 reference design is general purpose system (you can install apps for almost any purpose and browse web for more), high performance (well depends what you compare to), battery powered, complex multitouch input support and a screen with resolution we used to have our PC's not a long time ago (1280 x 800).
Lumping both under "embedded" does not really help anyone.