Considering that after 30 days the starter edition will be freely available to anyone with a Battlenet account this really isn't that big a deal.
I think it's clever marketing. You suggest that something might be "hard to get" and more people will want to try to get it.
I'm a little concerned about this though, Blizzard servers are already going to be strained with just the paying customers now when you add in all the freeloaders things might get hairy. I don't know about you but if I have to sit in a queue for 30mins trying to log in while dudes who haven't paid are busy knocking away I might get a bit bleak.
I suppose that could be moot if they have a separate server for starter editions (aka old beta server).
Otherwise it's a good opportunity to get you mates to try it out if they were sitting on the fence.
I think you might be onto something with the old beta servers idea, could explain why people on starter edition can only matchmake with other starter edition people. They must move your char & loot over to one of the lives servers when you upgrade.
If that is the case I just hope they have a starter server in the EU, since one of my friends want to see how the game works on his connection before he gets the full version.
im a little worried about d3, the beta didnt go so well for me as i thought it would, If i can get given a free pass and the game works well then i might get it but from what i played in the beta i wasnt as impressed with it as i thought i would have been. Felt too easy and the lag was bad. But guess we will wait and see how it is when they launch tonight.