PC World posted a news story that Microsoft has switched to an install-based licensing plan for the upcoming Office 2011 for Mac

While this change is bearable--given the prevalence of Apple's own Mail application--there's another change that, I feel, unfairly penalizes owners of multiple Macs. The Home and Student version of Office 2008 included three CD keys, each of which allowed installation on up to two Macs--that's a total of six Macs on which you could install Office. However, you could only use one copy of Office at a time; a network serial number check wouldn't let two copies with the same serial run at the same time on the same network.

As someone who owns five Macs, this setup was perfect for me: I'm one person, and I don't need to run more than one copy at a time. So I could install Office on all five of my Macs, and move my work easily between them by simply insuring that Office wasn't running on any Mac other than the one I wanted to work on.

  Office 2011 Pricing Penalizes Owners of Multiple Macs