Reader Kjeld Sorenson had a nasty shock and doesn't care to be surprised again. He writes:
I happened to have Disk Utility open the other day and much to my surprise I saw a warning about my Mac's hard drive--that it had failed something called a SMART test and wasn't reliable. First, should I replace the drive and secondly, how can I see alerts like this automatically?
S.M.A.R.T. is an acronym for Self-Monitoring, Analysis, and Reporting Technology and is a scheme built into hard drives, rather than computers. If a drive reports that it's failed this diagnostic test it indicates that the drive is on its way to giving up the ghost, not that it will seize up in the next couple of minutes. This should allow you plenty of time to back up your data (which you should already have been doing) in preparation for that drive's eventual demise. Of course, as in your situation, it's possible that it failed the S.M.A.R.T. examination weeks ago and is that much closer to the grave.
In either case, given how inexpensive storage is, I wouldn't ignore the problem. At the very least, get an external hard drive and clone the failing drive to it using a utility such as Carbon Copy Cloner or SuperDuper. That way you not only have a complete backup of your failing drive, but you also have a drive you can boot and work from. You can later replace the failing internal drive if you care to.
As for your second question, I agree, launching Disk Utility each day to check your drive's integrity would be tiresome. Fortunately there are utilities you can use to automatically monitor it. Starting with the least expensive (as in "free"), CoreCode has a free version of its SMARTReporter utility. Launch the application and it places an icon in your Mac's menu bar that indicates the health of your ATA, SATA, or eSATA drives (including internal SSD drives). USB, FireWire, and SCSI hard drives can't report S.M.A.R.T. status. It monitors your drives from time to time throughout the day and if it detects a failed S.M.A.R.T. test it issues a warning--a Growl notification, alert dialog, launches an application, or sends an email message. This version is out of date and unsupported by the developer, though it works perfectly well with Mountain Lion.
For $5, however, you can have the fully-supported version 3 of SMARTReporter (pictured above). This adds the ability to check for data I/O errors that may indicate a problem.
Bjango's $16 iStat Menus 4 is another worthy option. It not only monitors your ATA, SATA, and eSATA drives' S.M.A.R.T. status, but, in regard to drives, it can report how much of their capacity is being used as well as their read and write statistics. And iStat Menus reports a whole lot more about your Mac--it tracks how your CPU is being used, shows memory allocation, a network graph relaying information about sent and received data, includes a temperature sensor, and provides detailed information on your portable Mac's battery.
And then you can turn to the Big Guns--ProSoft Engineering's $99 Drive Genius 3 or Micromat's $50 (currently on sale for $30) Checkmate or $100 Techtool Pro 7. Drive Genius and Techtool Pro can not only monitor but also repair your drive (though no software utility can repair a problem with the drive's hardware). Checkmate is a monitoring application, but one that goes beyond simple S.M.A.R.T. status reporting. It will additionally check your Mac's RAM, laptop battery, volume structure, RAID status, the integrity of the hard drive's surface (looking for bad block, for example), file structure, I/O check, and Power On Self Test.