Two aspects of the up to 72-hour waiting period digitally purchased versions of Diablo III now undergo before full functionality are unintended, Blizzard tells Kotaku, and will be addressed "as soon as possible." The delay (which they say can be as short as one day) is to allow them to process credit card information before allowing unverified accounts the ability to buy and sell items and access areas of the game where commerce is conducted. But it is not intended to impede player's progress as it currently does. Here's word:

However, as an unintended consequence of these security measures, players who purchase the game digitally after patch 1.0.3 are temporarily being capped at level 13 and not able to proceed beyond Act I. We are working to correct this as soon as possible and will provide another update when we have more details to share.