After Michele's ordeal, the Virgin girl fiasco, and my own internal struggles with the asinine Yahoo/Flickr Terms of Service (basically your photos are theirs), I've decided to post a little blurb about the privacy settings in Flickr.
If you're posting photos that you don't want others to use I'd recommend going through your user preferences to make sure everything is set the way you want it. Here's a simple tutorial on what exactly the Flickr privacy settings mean:
Firstly, login into Flickr and go to preferences (click on your highlighted name at the top). Once there click the privacy and permissions tab. On the resulting page you will see a listing of the various privacy settings.
Global Settings:
Who can download your photos? This option sets who can download/view the very large versions of your photos (a feature available only with the Pro account). Unless you want to share your photos in their very large and detailed glory (say with family or friends) I would turn this to only you. The default is everyone can view.
Who can print your photos? The default for this feature is "Only You." When changed to "Any Flickr Member" this option allows other users to print copies of your photos using QOOP (a print company). Again, unless you want people to print your photos I would keep this at "Only You".
Who can blog your photos? The blog this feature is only available for public photos. Personally, I've never used this setting or Flickr blogs, but I assume it means you can allow other site users to post blog posts about your image.
Hide your photos' EXIF data? EXIF data is digital camera data. With each image is stored multiple details about your aperture settings, the lens you are using, your shutter speed, the type of camera used, etc. Flickr's EXIF data is quite extensive and tells a lot about your photos and your camera.
Hide your photos from public searches? There are tons of feeds and searches out there that use Flickr's API to search for images. Yahoo's Image Search is the biggest (most feed off of this) and it pulls photos off the Flickr website to external sites. This annoys the crap out of me so I've set this to "Hide your photos from site-wide searches on flickr.com?" and "Hide your photos from searches on 3rd party sites that use the API?"
Defaults for New Uploads
Who will be able to see, comment on, and annotate your photos? This allows you to set who sees your photos immediately after upload and subsequently who can comment and leave notes; by default your photos are public upon upload. However, in using this setting you can change the default to "Only You (Private)," "Your Friends," "Your Family," or Friends and Family. Once set whenever you upload a photo it will be private (or whatever your setting) until you determine otherwise. If you add a photo to a group, however, it is available to all group members regardless of your set privacy setting.
What license will your photos have? This is very important because it determines who can use your photos and how they can be used; this is what allowed Virgin Mobile to use the photo of the “virgin girl” in their ad campaign (though their legal downfall is the age of the girl -- she's a minor and to use the image of a minor in most countries you need parental consent). The default now is "no one but you" (copyright). But, there are creative commons options for those who would like to have more freedom in how they share their photos.
Who will be able to see where your photos were taken? This is only important if your camera has GPS. Like EXIF data it is an extra piece of info that tells people where your photos were taken.
Auto-rotate your photos? Here you can choose whether or not you want Flickr to auto rotate your images based on data stored in the photo (using EXIF).
What Safety level and Content type will your photos have? This works in conjunction with the safe search and can tell users that your photos are safe for viewing (i.e. no adult content).