What do you do when your platform already sells and launches video games? Make the platform itself a video game, naturally. Valve announced the beta launch of "Steam Trading Cards" today. The collectible meta-game lets you upgrade your Steam profile by playing games and collecting and trading their associated (virtual) cards.
The trading card system earns you cards for playing supported games, along with collecting and trading. Once you earn enough, you can craft a game badge, which can be used to earn rewards like profile backgrounds, emoticons, and Steam coupons. This also adds a leveling mechanic to your badges, in which you can earn XP to earn rewards like extra friends list slots and profile showcases. Joining the Trading Cards group will put you in a queue to get into the beta, and Valve will be allowing people into it in waves.
So far, the beta supports Counter-Strike: Global Offensive, Dota 2, Don't Starve, Half-Life 2, Portal 2, and Team Fortress 2. Valve promises it will expand to more games in the coming months. You can check out the FAQ for more details.