There are so many celebrity blogs out there that just take images. Is it ok to copy celebrity pictures onto your site? What about images in general?
No no no no no. Lots of people drink and drive, but it's still illegal. Check out "fair use" to see how much of an image you can take for free. There are some time when you can take an image if you're going to comment on the photograph, but you can't just take whole galleries for your own site.
Less important sites get away with using copyrighted content. But if you own an established site, avoid this.