Microsoft handles activations differently. When you hit the limit, you call them and they help you. When you hit the limit with EA, you call them, and they maybe help you. Yes, some versions don't come with activation limits.
The last one I ran into was a service pack 2 edition that had a 3 activation limit, after which you had to phone home, talk to a computer, and speak your cd key to get extras, the first three were automatic over the internet.