BioWare community coordinator Chris Priestly revealed in a post on the company’s official forums that the PC edition of Mass Effect will have an online validation system. Within ten days of installing the game, you will be required to register it through BioWare’s activation server.

If you buy MEPC, install and run the game the game will register automatically and you are good to play.

After 5 days the next time you start the game the system will automatically try to register. If you are connected to the internet, it will occur without you even knowing it and reset the 10 days.

If you are not connected to the internet, you can keep playing for the next 5 days. As you start each day, the system will keep trying to validate. If it connects and validates, the “clock” is reset.

Similar to the activation system that BioShock has, but not as annoying - seeing as you have an unlimited number of attempts to complete the process. Still not sure why they even bother though, considering that pirates who want the game will find a way of pirating it regardless. Happens with every PC release.