Steam keys are retail keys taken from retail merchants that can be applied to steam, mostly scanned. Those keys can be region locked or blocked or even contain a censorshipped game
Steam gifts are directly purchased and gifted to you. They cannot be blocked or locked. You'll not get a censorshipped game if you live in for example Germany and the gifted game is bought in the US.
There is no problem with steam gifts except of being shipped a bit slower because there is no automatic system (I'm aware of).
Actually, there's a few games that get blocked or locked. One example was Borderlands 2 which Russian traders sold at a cheap price: When it was released, it was locked to Russian servers only(as in you couldn't play with people in the rest of the world for co-op). They gave the players with the RU copy a ROW copy after a while though so it's fine now. Another was Banished, wherein people purchased Russian copies of the game and it was retroactively blocked from being run even when people had already activated the game and played it.
@OP: For Steam Gift trading, you're in the clear for the most part. Most traders take precaution to only trade ROW versions of the game but some problems do happen where games/gifts in the inventory are retroactively marked with a region and have region locks added onto them.
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It's recommended to activate the game you receive as soon as possible since games are known to retroactively be region locked with activation locks. Those that activate the game before a region lock are more than likely to be fine for the most part; it's just if you don't activate it and it later gets region locked, you could be blocked from even activating the game on your account. Recent example: Valiant Heart
Edit: I want to point out that Banished was reverted back after people complained about it being retroactively locked. But this set the precedent that Valve can lock gifts even after you've played it months or years in the future.
One thing that is yet to happen is with The Witcher 3 RU copies. Currently, there's no activation lock but it is tagged RU. The devs say they won't put a OnlyRunIn lock on it unless the regional trading goes overboard. :/
Also, there technically is an automatic trading system but it's only for within Steam trading such as with TF2/CSGO/Dota2(?) keys for games. A few sites like dispenser.tf use some sort of bot that utilizes the function to automatically do trades for you at preset prices without you needing to be online :/
[Edited by CombatWars, 9/1/2014 10:47:30 AM]
Steam keys are retail keys taken from retail merchants that can be applied to steam, mostly scanned. Those keys can be region locked or blocked or even contain a censorshipped game
Steam gifts are directly purchased and gifted to you. They cannot be blocked or locked. You'll not get a censorshipped game if you live in for example Germany and the gifted game is bought in the US.
There is no problem with steam gifts except of being shipped a bit slower because there is no automatic system (I'm aware of).
You can make links to the gift when you make one, so when someone uses that specific link they get the gift.