One of the nice goodwill things I liked about Steam was that when I registered my original copy of Half-Life, they gave me all the extension packs for free. Might have been because they couldn't tell by the CD key whether I had just Half-Life or the pack that included them, but I didn't care.
If you buy the HalfLife2 orange box ulimate set and already own HalfLife2. Then you can give your old HL2 copy to a friend for free.
One of the concerns is that people like microsoft wouldn't bother doing the above.