Just after the launch, Blizzard got quite some problems. Due to the overwhelming success (240.000 units sold on day 1!) the servers couldn't cope with the amount of players. Also after the European launch similar problems were noted. Luckily the publisher acted quick and well by amongst others giving away free gametime, adding new servers and releasing patches. Most of the biggest issues by now seem to have gone away but there are still some problems now and then to log in and also the lag hasn't disappeared. However, this isn't a problem that can't be overcome and in fact it's common with MMORPG's. The makers were probably surprised by the huge amount of subscriptions (after the first month you need to pay €12,99 on a monthly basis to keep playing) but with the hype that was surrounding this game, they could have thought of that beforehand.