Simon,

"Technically yes it is an infringement. The
strange thing is that in law inlining the
image in a page is considered less serious
than if you were to copy it over to your
server and host it from there - even though
when inlining not only are you breaking
copyright but you are also sending them the
bill for the hosting!"

Also, a number of web pages include in their copyright notice
language specifically prohibiting this practice. Often this
language states that you can link to the page, but not directly
to the image(s) found in it. If you find such language in a web
page, it indicates that the person or company, who own it, is
more likely to come after you for this practice than others.

Best regards,

Paul
Baton Rouge, LA