Other observers said that as Microsoft moves toward a hybrid licensing model with both installed software and hosted services, it will need tools like WGA and OGA to continually scan customers' computers and verify that they're covered.

But it has to be careful, warned Lauren Weinstein, an IT consultant in Woodland Hills, Calif., and co-founder of the privacy advocacy group People for Internet Responsibility. "Microsoft is starting to tread a thin line that has quite an abyss on either side," Weinstein said. "If people feel that Microsoft is acting too aggressively, they'll find some way to go to other products."