This issue alone will make-or-break the deal for me. If Diablo 3 (or Starcraft 2) ships with overprotective DRM, I may have to pass on this masterpiece.
For those who don't know, lemme give you a quick rundown of DRM.
DRM = Digital Rights Management. Generally, it grants control over your copy of the game to the game creators (in this case, Blizzard). DRM has varying degrees of restriction. Serial keys are a very light (and in my opinion, acceptable) form of DRM; they control who has access to online benefits. Many games today employ copy protection DRM; the original disc works, but CD-Rs do not. EA recently exerted too much control over Spore (and several games preceding it) by restricting the number of times you can install the game ever (currently, I understand the limit to be 5 installs).
I am OK with serial keys. These keys at least somewhat ensure that my copy is my own. Blizzard also uses these to enable/disable access to Battle.net (great for kicking off cheaters/spammers).
I am NOT OK with games that require online validation of my game to play SINGLE PLAYER (such as Portal or Half-Life 2); I am not always near an Internet source (particularly on my laptop), and I want to enjoy something when Internet is not available.
I am also NOT OK with games that install rootkits or other programs that are designed to watch me, watch what programs I run, and report back statistics to the mother ship. SecuROM (EA's favorite DRM choice for many of its games) is the primary offender here.
The primary problem with DRM is that it is designed to stop piracy... but it never succeeds at doing that! Spore was leaked/pirated before it was even released, and it is a very recent game. Blizzard needs to understand that Diablo 3 will be pirated. That is an unfortunate circumstance in today's world, but any precautions should not royally annihilate the paying customer's experience. Today, pirates are enjoying DRM-free (aka hassle-free) copies of Spore, while the customers who actually gave EA real money have to deal with installation limits, SecuROM, etc.
Another big problem with DRM is that big companies have to maintain DRM servers. Microsoft, Sony, Yahoo, and now Wal Mart all sold DRM-locked music until they decided to stop; they were gonna shut down the DRM servers until customers voiced their rage about being unable to transfer that music (or ever download it again); the servers were kept running a bit longer. I don't know about anyone else, but I still have moments of nostalgia where I like to take my ancient copy of Warcraft II, stick it into my computer, and play it (no matter how old they get). If they required DRM servers to be running, they wouldn't work anymore.
DRM essentially changes purchases into rentals. No one can really purchase EA's Spore; people can only rent it as long as EA permits. Meanwhile, again, pirates (the ones who DIDN'T pay for the game) continue enjoying it with no problems.
Blizzard, be gentle with DRM. Don't require the disc to be in the drive. Don't have the game phone home just to play Single Player. Here is the point: the game will get cracked; the game will get pirated... but I will still go out and purchase the game. There are more honest people in the world than EA gives us credit for. I purchased Diablo 2 despite knowing I could have downloaded it illegally. Give value to your paying fans; don't make piracy the more enticing choice.