Just been to a friend's website and discovered that it was preventing me from right clicking on anything.  They obviously decided to add the bit of javascript to the page to prevent naughty people from downloading the photos they'd put up there. However, preventing right clicks is a very bad thing indeed.  Here's why:

1. If I really want to download your pictures I'll be able to do it by other means
2. I need to select text so that I can:
   1. Bookmark in delicious
   2. Craft a tweet using the bit.ly sidebar
   3. Search for that text in Google
   4. Get the definition from my built-in dictionary
   5. copy the text into my blog editor so I can link to your website
3. Maybe your page is broken in Firefox, and I want to view it in Safari or Internet Explorer
4. Maybe I'm a web developer and I want to inspect the html element under my mouse so I can see how you've built the page

The point is that the context menu provides me with more than just "Save Image As...", and you're making things very difficult for me to use your site if you don't let me use any of those tools.