I was just wondering if anyone had any insight on what sort of stance Blizzard takes on situations where a fan was interested in making t-shirts or other paraphernalia with names or logos that reference the games.

Do they attack with a vengeance or are they generally fairly lax with things as long as people don't try to pass of their stuff as "official"?

I ask because I was bored and made a couple Diablo 3 t-shirt logo prints just for kicks and they turned out kind of decent.

We regularly contact people attempting to sell goods with our copyrighted materials on them with cease and desist orders. It's not something we're very lax on.