Quote Originally Posted by Otlecs
They do indeed use IP addresses as a flag for investigation, but not quite to the extent you perhaps think.

If the account logs in from, say, Tokyo at 1pm GMT and then again at 3pm GMT from London then it's a clear case of account sharing and they might want to have a look.

But it's not a flat "multiple IPs = ban", and I can say that with absolute confidence
If this was an issue my buddy who spent 2 years in Germany and shares an account with his old man would probably have issues... since they consistantly overlog each other (not even a few hours difference, one logs out in Iowa, one logs in in Germany). The IP may be something that they use to support their decision to ban int he end, however no one can know that for a fact since Blizz doesn't share WHY they banned you, they just do.