Finding a flickr account from a picture URL

Very easy:

Enter http://www.flickr.com/ , then paste the name use by  the person who took the picture and you get all the photos that exist in the site from the same person.

Here is an example with a person named jonholato

http://www.flickr.com/photos/jonholato/

If you have the URL then press on it. When you get to the flickr site you will see the user name , and you will be able to see all his posted answers.

Very good example of how finding the photo mentioned by Dinosaur Jr.

The link leads (of course...) to "Dinosaur Jr. at the Troubador in Los Angeles on April 22, 2006" 

http://www.flickr.com/photos/carradine65/

will lead you to his 1775 photos (as of 31.10.06)

You can do it this way...

As Yaniv says, you can get the photo id from the image src:
http://static.flickr.com/55/133527964_911184289d_b.jpg

For this photo, the id is 133527964.

Use the photo id in this link:
http://www.flickr.com/photo.gne?id=PHOTO_ID

You will be magically transported to the photopage :o)

(I see that it is a photo of your namesake, Dinosaur Jr) 

DinosaurJr - If google still hasn't indexed the pages you're looking for, you can use flickr's api. 

Simplest way to do it is to go to http://flickr.com/services/api/explore/?method=flickr.photos.getInfo (which is the api explorer page for the function flickr.photos.getInfo), and fill the photo_id field with the value that Yaniv described above (e.g., 133527964).

After you click the "Call Method..." button you'll get an XML result.  At the bottom of that result you will be able to see the url for the photo page.  It will be something like:

 <url type="photopage">
             http://www.flickr.com/photos/carradine65/133527964/
 </url>

This is the page you're looking for.