With the immediacy of pictures from smart phones and point and shoot camera's, the professional headshot is becoming a thing of the past. I say 'stop the madness'. A quality headshot requires professional lighting, the correct lens selection, an environment that best suits the subject and a photographer with the knowledge to follow through. Everyone has a best side, your best side deserves the attention of a pro.
Reference photos can be very useful in illustration. They can serve as base and be modified to further to capture the exact message. Above is a photo of my wife posing for an illustration used in Tomahawk Live Trap's Control Pole instruction sheet.
I often receive logos and photographs from outside sources that are too small/lo-res to work in a print document. The rule of thumb is that a file needs to be 300 dpi at its displayed size. A jpg or tiff will do. An eps for print is preferred. 95% of the time, anything pulled off of a website will not work. Knowing this information will not only save time