From the comments, Scott Sumner

The Danes have an escape hatch that the Swiss did not have, they can join the euro whenever they wish. Thus the Danish central bank can pocket huge profits from European speculators for as long as they wish, and then if their balance sheet gets uncomfortable they can join the euro at the drop of a hat. There are very few countries in such an enviable position. (Even so, I think the peg is a bad idea–they should let their currency float, as the Swedes do).