According to this AngryPixel report, the PC version of Mass Effect will only allow you to activate the game three times and will self-check its key every 10 days. From the site:
According to Derek French, Mass Effect, scheduled to arrive on the PC this 28th, will employ the same SecuROM online activation system that was initially put into Bioshock, allowing the buyer to activate his copy of Mass Effect for 3 times before politely asking to him / her to go to hell, that is, contact the customer service “helpline” to get it reactivated. And while the game itself wouldn’t require the DVD to be physically present in the drive, it goes one step further and phones home every 10 days and re-authenticates just to make sure legit customers are not the worst form of criminal scum publishers swear we are.
The authentication, which will be initialized every time you run MassEffect.exe, will send the CD Key and a unique machine identifier to the activation servers, which will be cross-referenced with the data that was sent when the game was initially activated.
Blimey. More through the link.