How to prevent someone on stealling your picture

Want to prevent someone from stealling your picture on your Friendster Myspace. Etc... profile?
yes you can prevent it.. how? by putting watermark on your picture

Tip

just put the url or your email address on the picture.. specifically at the middle of the picture to prevent editing.

Here is a tutorial on how to put a watermark on your picture using photoshop..
http://graphicssoft.about.com/cs/photoshop/ht/apswatermark.htm