Mass Effect uses SecuROM and requires an online activation for the first time that you play it. Each copy of Mass Effect comes with a CD Key which is used for this activation and for registration here at the BioWare Community. Mass Effect does not require the DVD to be in the drive in order to play, it is only for installation.
After the first activation, SecuROM requires that it re-check with the server within ten days (in case the CD Key has become public/warez'd and gets banned). Just so that the 10 day thing doesn't become abrupt, SecuROM tries its first re-check with 5 days remaining in the 10 day window. If it can't contact the server before the 10 days are up, nothing bad happens and the game still runs. After 10 days a re-check is required before the game can run.
They made a FAQ about the copy protection, heres a quote of the most relevant stuff
Q: Why does MEPC need to reactivate every 10 days?
A: MEPC needs to authenticate every 10 days to ensure that the CD key used for the game is valid. This is designed to reduce piracy and protect valid CD keys.
Q: What happens if I want to play MEPC but do not have an internet connection?
A: You cannot play MEPC without an internet connection. MEPC must authenticate when it is initially run and every 10 days thereafter.
Q: What happens if I install and activate MEPC with an internet connection, but then do not have an internet connection after 10 days? Can I still play MEPC?
A: No. After 10 days the system needs to re-authenticate via the internet. If you do not have an internet connection you will not be able to play until you are reconnected to the internet and able to re-authenticate.
You can only install this 3x on the same PC and then it is no good. remember Bioshock this is worse.
Also what happens if the servers go offline for a few days a week for good. Well you dont get to play this Single Player game at home, You will have a coster to sit your drinks on.
DONT BUY THIS GAME!!!! IF YOU PREORDER IT CANCEL ASAP. YOU HAVE BEEN WARNED.
Also if you like join the forum and pst your opinion about this issue.
Read from BioWares Mass Effect forums about this issue.