Personally I think Blizzard has it right. There is very little control or moderation of single player or LAN games. But there are undeniable benifits to playing online (esp. Diablo II). They validate keys once you've logged onto battle.net. I'm fairly savy in the warez\cracking\hacking circles and I know of no way to abuse that system short of stealing someones CD Key, at which point it is reported and banned.
Kuddos to Blizzard.