True about losing one's number, but you can redirect your home number to your (Spanish, etc) mobile.
There are actually other SIMs. There is an Italian product called a WIND SIM which gives you very cheap GPRS and very wide roaming. It's a bit hard to get without having to go to Italy, but once you have it regged you can use it anywhere.
Once I found a website (can't find the URL right now) selling a SIM card for just about every country in the world, and the key thing was that you didn't have to go there to initially register it.