It is probably too expensive (development wise) to scale for this many concurrent users as it will only happen once (or twice in case of expansions) during the whole lifetime of the game.
"Expensive" is incurring a tremendous amount of bad PR for a game on launch day. "Expensive" is having the launch of one of your flagship games be forever used as the butt of a joke. "Expensive" is turning your own customer base against you by having people who took days off work or stayed up until well after midnight to play one of the most anticipated games of the last decade being thwarted in their attempts. "Expensive" is people deciding to put off their purchases, perhaps forever, because they see the problems people are having. "Expensive" is having your brand reputation dented to such a degree that it affects future sales of all of your games.
What do you think this incident reads like in Vivendi's annual report? I'm thinking "We made a few more mountains of money with the enormously successful release of Diablo 3. Fans love it and monetization is six times previous records for the series a per-copy-sold basis or 200 times higher per copy played."
WoW also had launch issues. Players complained. Money hats were made.
In the near term Blizzard isn't going to be going out of business, nor is it going to have a shortage of money hats. But make no mistake, this is a serious issue and it has tarnished their reputation. They still have plenty of excess reputation at the moment but if they continue to take a cavalier attitude towards customer satisfaction then there will be another incident like this, and another, and another, until it really starts hurting their bottom line in a way they can't ignore.
Did it really tarnish their reputation when SC2, WoW, or DiabloII launched? It's such a transient thing that seriously suspect that they could do this forever and never effect sales in the slightest.
Ya but sometimes you just don't know who's in charge of making these decisions. I wouldn't be surprised if someone came out and said this was a calculated business decision. Nothing surprises anymore.