Spain is in some serious trouble and there are some that say Spain and other EU countries are going to drag down the Euro. Some even speculate the end of the Euro may not be too far off. Using one currency takes away Spain's ability to devalue its currency and thus make traveling to spain attractive (and a bargain) as well as being able to increase exports as they would be cheaper.
http://finance.yahoo.com/banking-bud...leground-spain
Then you will find all the currency traders drooling at the prospect of $1 = ?1.
http://www.globeinvestor.com/servlet...82165/GIStory/