The PC version of Mass Effect is going to require an Internet connection to play as the game comes with a copy protection/activation procedure that requires the Internet to go online and activate your copy.

Gamers will be able to play Mass Effect for 10 days, but the game won't start up after this period until the software is able to go online and register your copy.

Chris Priestly, Community Coordinator for Bioware, said on the official forums;

“To clarify:

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.

So it is not "at 10 days and if the servers aren't working you're screwed". There is a large window (5days) where the system automatically tries to re-validate to prevent last minute problems”

This shouldn't be much of a problem, since most people have an Internet connection these days.