Ciao,
for the ones who are interested there was also a discussion in AVRfreaks
http://www.avrfreaks.net/index.php?name=PNphpBB2&file=printview&t=66583&start=20
I recommend You to use an industrial grade SD card if You want to reduce data loss risks.
For example, but there are many others:
http://www.cactus-tech.com/product_05_b.html
Ciao,
Marco.