Steam's feature of allowing users to gift and trade game keys has indirectly created an entire industry. Key resellers like G2A have always operated in a sort of grey market area due to a considerable amount of payment fraud that they typically turn a blind eye to. Valve's new gifting policies are designed to make gifting easier for the consumer but may also hurt resellers and overseas gamers.
The update has three main changes. The first is the ability to schedule gift transactions. This means you can buy a gift in advance and have it delivered to a friend on their birthday or whenever you want. The next feature deals with declined gifts. Previously, if a user didn't want a gift they received, it would eventually be returned to the seller's inventory and they would still be out the money. Now, the recipient has the option to decline the gift and the sender will automatically get refunded. The third feature has created the most controversy. For all transactions following the new update, gifting across countries won't be available if there is more than a 10% difference in price between countries.
This new rule, while written to sound like it makes cross-country gifting easier, is actually a serious blow to key resellers. They typically buy keys in volume from countries where they are cheap. Then they can resell them in countries with inflated game prices and profit on the difference. Think of it as arbitrage in the game key market. While Valve is certainly trying to cut down on the payment fraud associated with key resellers, this change may also have negative consequences for normal gamers with international friends.
Games are relatively cheap in the US compared to many places like Australia and South America. It was easy to get an American friend to buy the game at the cheap US price and then simply gift it, but this won't be allowed anymore.