Opt Out of Photo Searches
If you are a flickr user, you might have noticed that both Yahoo and Google search engines as well as some third party software can search for your photos. If you would prefer to exclude your photos from from public searches either on Flickr itself and/or any third party software that accesses Flickr via the API (including Yahoo! Image Search). Go to this page on Flickr to opt out. You can select to hid your photos from site-wide searches on flickr.com and/or hide your photos from searches on 3rd party sites.
To Opt Out of Searches, Head to this Flickr Page
You will still be able to see your photos on third party systems as long as you are logged in to Flickr.
Or Set some or all Photos as Private
If you prefer to just keep your photos private and control who can and can't see those photos, you can alternatively mark all of your photos as private by going to the "organize" tab in flickr, selecting permissions and changing who can see and comment on those specific photos.
For a complete listing of flickr hacks and tools CLICK HERE
Here are some other Flickr "hacks" I've recently written about:
Flickr Hack: Show All Flickr Contacts
Easy Flickr Hacks: Surf Your Photos
Blog Hack: Custom Flickr Search for your Blog
RSS subscribe to your Flickr Contacts Favorites
Tag and Organize Photos with iTag
Cool Flickr Related Tag Browser Tool
Four Ways to Track Statistics On Your Flickr Photos