I started going to cemeteries in geneology searches. As I went thru the cemeteries I realized how much the stones wear down (and all the other factors - cemeteries not being kept up, vandalism, etc) and that someday you wouldn't be able to read those stones.
I also realized what great things people were doing by taking pics, and volunteering to take pics, for people who were looking for their family and couldn't get to the area.
So...I starting taking pictures myself. Now that we have digital cameras all it costs me is my time. And the results are great...people find family they're looking for and most importantly, those that were buried in the cemetery and the stones were put up for are not forgotten.