How do people have lots of gifts from one game

Buying them ?

I asume he bough all that stuff on a sale ... or during a price glitch

Why do you care?

probably use them as currency for trade

trading http://www.tf2outpost.com/user/673625
+some weird choices, for example, multiplayer games are easier to trade, it will be hard to trade all those witcher 1 for 2 keys :O

These are the marks of someone who takes trading seriously, nothing more.

well, judging by his profile, and comments he is obviously a trader....so...off the top of my head, I am going to go out on a limb and guess he has them for trading? Most of the games have been on sale recently, so he prob picked them up then...but, to be honest...and I don't mean to sound like a jerk, but I don't see what it matters to anyone what someone spends their money on or has in their inventory.. :/

I once bought 8x Tropico 4 when there was a pricing error.

simple, he is a real trader.

To trade them? It's pretty obvious. :)