I always take the approach of not being afraid to add an extra 10 euros or so to my expected usage, on the basis that I can always sell the card on eBay when I get back.
Obviously there are issues with the SIM card being linked to you, but since the recipient probably wants a card they can burn up and then throw away, this shouldn't be a problem.
+Steve
[size=2]Steve Gold
PO Box 1014, Sheffield S10 5YG, UK
Home mobie: Telefonica O2
Other UK mobiles: 3, Vodafone, Virgin
Foreign SIMs: Toggle (multi); Germany (Fonic); Poland (Orange PL);
Skype: stevewgold