Bilking people of all ages is a huge business, and many scams target older adults. The phone and regular mail is the way many organizations that are not really legitimate con us into giving money, get our credit card numbers, and begin sending mail to us with pictures and stories that pull at our heart strings.
Be careful and be sure to research any organization before you give them a cent. Many of them support a huge administrative staff -- rather than giving most of their funds to actual people in need, their administrative costs take up most of the money donated. It's better to give to organizations that have a small overhead and give most of their budget to their targeted recipients.