What makes you say that? if this site itself was putting them up (rather than members) maybe it's "illegal" but this is an area of user-content, similar to say, Youtube for example. It's about on par with putting up copyrighted material there (which happens all the friggin time and youtube itself depends on people breaking that "law" in order to thrive).
I wonder how bing keeps selecting those images. If they are random (probably), well they are very nice to be random then.
I don't think they are random since they have those pop up notice things when you hover over different parts of the image.... someone obviously has to put those there.