I've done it both ways
A) used that persons email when buying it
B) Buy the key as new, then logged on once to confirm its ID#
-i guess technically against the terms, but when the 2k's were still available to buy it was fun being more specific on what the prize is when contests are on.
but offering up a key because your bored of the game isnt the same as buying one for someone.
that is one less sale for badspot to earn on.
in fact why dont we all just get together and recycle our keys. the entire first 5k keys can just be given away to the next generation blockland users when we get bored. then they can pass it on to the 10-15k'ers