Yeah you could do that with a flickr account until last year when they changed things so that if you replace an image it gets given a new URL. Something to do with server caching they say, but the change came at the same time that there was a user revolt over Yahoo using flickr content.
Most leeching of images from flickr is done via their API where sites pull off images based on keywords/tags, either by the searches or RSS feeds. Here is a typical example of 'tarting up your website':
http://www.viaouest.com/galerie1566.html
the size of the displayed images probably just puts it into the realms of 'fair-use'.
Actually this automatic pull from flickr is quite a dangerous thing for the website to be doing irrespective of any copyright issues, because they have no control over what gets tagged, they have no control over what they start displaying.
For the page in question one could tag anything with 'Laval' and it would appear on their page. Imagine some one posting a photo of their kid in the bath tagged with the name of some village. Additionally flickr allows people to post HC porn so long as it is filtered as such, but many people don't filter it properly so it is also likely to be appearing on these sites too. Not good.