You can't trust flash drives

I set up AX64 Time Machine (http://forums.majorgeeks.com/showthread.php?t=292781) to do its hourly backups of my wife's PC to a Sandisk 60GB flash drive and for three days all was well with 30GB of 60GB being used. Then I noticed the backups had stopped and it turned out that the flash drive had become corrupted and was inaccessible. AX64 on the other machines here is backing up to external HDDs and after more than a week now there haven't been any problems with any of them.

I have had flash drives fail on me before and do not consider them a safe medium for anything you consider important.

I was able to reformat the drive in Disk Management by creating a new simple volume and not selecting quick format. It took 6 hours but I shall never trust it again.