Putting someone elses art on your personal website/myspace. Should you ask the artist first or...?

Question

(Sorry for double posting. Pretty sure I put this in the wrong place the first time.)
Hey, I'm having a problem trying to find information on this. My friend found a picture she made for her website. It, was on someone elses myspace. She was really pissed. I feel stupid for not knowing. Is this considered "Plagiarism"? If not, is there a word for using someones art like that? No link, no permission, no name?
Honestly I go around finding pictures that I want to add to my myspace. Usually I pick old classical paintings, but I had at least one new one there too. I could not find a name for the artist or anything, So I just put a link under it *AND DELETED IT RIGHT AWAY BECAUSE OF THIS*

So what's the deal? Posting pictures on myspace? Or just sites that are really public like that, not selling or saying it's yours? Does artist need to be contacted? Or should you just have links and names and what not?
I respect artists, so I'll look stupid asking this

Answer 1

Unfortunately yes, the use of material that are not public property can cause you grief.

People will go to lengths to "protect" their material. Some may do this for proprietary purposes, and to control the use. Others simply want a fee, to be asked and to treat this art as a good to be purchased.

Answer 2

In US all work is copyrighted as soon as created by an artist, so using it without permission is not only wrong but illegal. If an artist or their estate finds out they can sue you, which will cost you a lot of money. Just look at all the illegal downloading of music and the lawsuits.

But usually if you ask first the artiost will let you use it as long as you mention their name and give them a link.

Answer 3

YES!

Especially if the artists work is copyrighted!

Answer 4

Go to this website and these books will tell all.

http://www.nolo.com/article.cfm/pg/3/objectId/F661972E-290A-4E01-83926E1AF5BDF8C4/catId/FD8C060B-5DD4-4809-A53ECCF6BBD87E32/310/ART/