Originally posted by tybeck I tend to keep my cards < 4 GB to decrease my chances of losing a large number of photos due to a stupid card read/write error.
Coming from an imaging and IT background we tend to regard all data as precious. Large media tend to be a riskier option unless you have backups or nice striped RAID file servers! So where possible, backup often. If not, use smaller media but more of them so that ALL is not lost when one fails.
We've had a number of near misses over the years and usually with high capacity (for the time) media. Most failed due to physical issues like tracking or head misalignment. Some were physically damaged by dropping. In all cases, recovery was possible, but expensive.
Newer electronic media like flash don't have those issues, but they do have issues of static charge, corroded contacts or data rate/clocking (eg mismatched RAM in a PC causes no end of trouble). Heat/humidity can affect any electronic device as well.
And testing out of the factory may not always be perfect - I have one retail contact who sold a fairly cheap non-brand name DVD player that had a 70% failure rate. It was made on the same line in China as the equivalent brand name device, but the brand name device had a 1% failure rate. Reason - the brand name added a rigorous QC step that picked up the fault.
Correct handling is also important, and its may not be you! Many retailers haven't got a clue about handling these devices, so they'll touch the contacts with their greasy fingers, leave them lying about on their bench tops, and generally ignore some basic rules. We don't mistreat out lenses that way, and we certainly treated film with more respect.
So Tybeck's suggestion of <= 4GB cards is sound - you reduce your risk of data loss and are more likely to keep all those images perfect. And the brand name is also important - SanDisk make most of the worlds flash memory.