Of course, a digital camera is always great for taking family photographs. Millions of people do that every day. However, for the genealogist, a camera can serve as a multi-purpose tool. It's even better than a Swiss Army Knife!
My favorite use of a camera is for snapping pictures in a cemetery. It serves as an automated notebook, recording the transcriptions. However, even better, the resulting images serve as source citations for the records you keep. I cannot think of a better source citation than an image of the words that were etched in stone. Of course, you will want to record the date, too. This is easy to do with most digital cameras that will optionally record the date and time on every picture taken.