Valve has confirmed that they are beginning the beta process for Steam Trading Cards, which will be used as collectibles and can unlock special rewards, including game coupons and downloadable content.
According to the official Steam Trading Card Website, players will be able to earn trading cards though playing a variety of Steam games. Up to half a card is earned by actually playing a game, and the other half of a card must be obtained through collection. Once Steam users start getting sets of cards collected, they can then turn these cards into a badge. These badges will then show up on the player's profile, and will randomly generate a reward. These tradable rewards can range from special profile backgrounds and emoticons to game coupons. Gamers will be able to level up badges and collect the set over again to earn additional rewards and bring up their Steam level. When a player levels up, special bonuses are given like extra friends list slots and profile showcases.
Steam Trading Cards are acquired independently from a game's achievements, and currently are tied to a player's playtime within a game, though that may change in the future. Current titles with Steam Trading Cards are Team Fortress 2, Portal 2, Counter-Strike: Global Offensive, DOTA 2, Half-Life 2, and Don't Starve. More games are expected to join the program later.
The concept certainly is a fun idea, and gives gamers another unique achievement to hunt for. As Valve says themselves in the program's FAQ:
"Many games have achievements that are grindy or un-fun to get, and we want the act of getting game cards to be fun for all users in games.We also don't want to push users to cheat or use achievement-unlockers in games in order to get cards, since that devalues achievements and isn't that fun either."