Valve is making it even more difficult for region-hoppers to get Steam games at a discount.

Steam's region-specific pricing means that the cost of living and other factors can make the price of a game vary from country to country. While it is still up to publishers to set prices, regional pricing is primarily intended to make games fairly available to those who would normally have to pay higher prices. Despite its intent, regional pricing has long been used by those who want to purchase games at a lower price than they would pay in their home country.

As SteamDB noted, the latest change means that you can only change the country of your Steam account once every three months, and Valve is trying to crack down on those who exploit cheaper prices in other countries. Last summer, Steam made life more difficult for VPN users when it began requiring payment methods registered in the country where they were trying to make a purchase. You cannot "buy Half-Life from Argentina with a U.S. credit card.

Seems like a bit of an unnecessary addition, given that it is already difficult to change countries on the fly, but perhaps people were still getting around the system easily. It won't affect most people, but I can't imagine many people going to a different country more than four times a year.