Run the following:

$ sudo smartctl -A /dev/sda | grep -P 'Load_Cycle|ATTRIB'

And see something like this:

ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
193 Load_Cycle_Count        0x0032   100   100   000    Old_age   Always       -       6038

The last value is the number of load cycles. A laptop hard drive typically has a lifetime of 600,000 load cycles. If the count is increasing by several thousand per day (or even several hundred), it may be cause for concern.

For information and how to fix it, see http://lwn.net/Articles/256769/