Hi people,
just thought i'd share this for all the 360 owners out there who like to dabble in the xbox live arcade scene.
Basically you can get all your games half price, and not only that, you can do this legally. (or at least like a sneaky ninja)
What you need:
O- 2 xbox's with xbox live (internet connection essential)
O- 1 friend (preferably with similar gaming tastes)
O- 1 memory card (this is optional just saves time when recovering gamer tags)
How it Works:
Basically, when you buy an xobx live game, you can buy it anywhere. On your xbox or a friends, any xbox you can sign your profile into you can buy an xbox live arcade game.
When you buy a game on xbox live arcade, the licence for that game is then registered to that xbox
if you have your profile loaded onto your friends xbox when you buy a game, the licence for that game is registered to that xbox.
Then when you go back home, and recover your gamer tag back to your xbox, the game you bought can still be played on your xbox with your profile, as long as you have connection to xbox live.
And your friend can also play that game as the original licence is on his/her xbox
Hints & Tips :
O- If you or your friend have played alot of games, changes are your receovery of your profiles form one xbox to another might take, a long time. To counter this you can copy your profile to the optional memory card i mentioend earlier to save time.
O- Remember to buy games on your friends 360 while signed in with your profile on his/her 360. To ensure the licence can stay on thier machine and allow you to go home and still play
O- If you have games already bought but still want to share, they both you and your friend will need to change the licence's option on the microsoft 360 website. Warning you can only change your licences once per year, every 12 months.
O- Warning if you or your friends console dies and can't be fixed then you will need ot wait another year or whats left of that licence period before you can get the game recovered since can only move licence once a year. Though if you just get a red ring of death, its usually fixable with the heat sink gel kit.
Thats that guys, hope some of you guys find this helpful.
I agree this is a bit of a ... shall we say 'grey area' ..... Its not illegal, its just technically, quite sneaky... and maybe not for everybody. However, having said that.. its a feature microsoft actually allows.
You can after all legally install a game you want to play on any console... like if you visited a friend or family member miles away or in a different country and deciede to buy a game while you visited.. it would be unfair for microsoft not to allow you still to play the game once you returned home from said visit.
I see this as a loop hole, made for people who have these visits to friends as an example or similar situations. The fact that it can purposley be done to acheive 50% price of games for me is a bonus 
for those who aren't sure wher ethe 50% saving comes from, its basically being able ot share games so you still need to buy the games full price but oyu can both share and still get all acheivements for them.
hope you guys can make some sense of this, for those who couldn't morally do this. Technically its just a loop hole.
Have fun guys. let me know if you figure it out.