The following is right off the Yahoo!PayDirect website (some irrelevant parts have been cut out):

Yahoo! PayDirect is a tool that allows you to send and receive money via email.

Secure -- With Yahoo! PayDirect, you will no longer need to expose your credit card information everytime you shop online. Yahoo! PayDirect can process the payments for you securely.

Convenience -- Yahoo! PayDirect eliminates the need to write a check, the inconvenience of sending that check in the mail, the hassle of depositing the check, and the pain of having to wait for the check to clear

Fast -- With Yahoo! PayDirect, payments are instantaneous!

The Yahoo!PayDirect page is easy to use. If you are already registered with Yahoo!, you only need to create a second password for security purposes. If you aren't registered with Yahoo, the Fool encourages it anyway, because it's a site with great features and services like games, email, maps, etc.

Once you are registrated, Yahoo! requires you to enter your Social Security number once. This is for identity verification. Again, they are secure. Then, you may send your donation. All donations are enabled by HSBC. All information is securely processed through Yahoo!

the Fool will NEVER see any of your personal or credit card info.

With this in mind,
Go for it!