It doesn't sound like a big deal. Connect online, activate and then play. However, Mass Effect will constantly check with a PC every 10 days for an internet connection and when a connection isn't found, Mass Effect will not start up. BioWare's Community Communications Coordinator, Chris Priestly, explained the process in the official Mass Effect Forums:

"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.

If the system cannot connect to the internet after the 10 days, you will not be able to play MEPC until you are connected to the internet. Once you reconnect to the internet and try to play, it will re-validate and you can play as normal for another period of 10 days as before."

Essentially, a computer with Mass Effect installed will check every 10 days for an internet connection. It'll be a transparent process however, because the game will check for a connection without any sort of human input and when a connection is found, the game will simply reset the 10 day timeframe. This odd process seems to be a unique method of battling piracy, because the game can simply find and detect a cracked executable, which would determine if the game is a legitimate copy or not. Just a theory, though.

How about legitimate customers who don't want to put a DVD in the drive every time they want to play? Well, they won't need to; the DVD is used only for installation and it isn't required to run the game. So, don't fret, this doesn't sound like another BioShock fiasco.