Tattoos (Copyright?)

You can use anything copyrighted as long as it doesn't reduce the holder's revenue (pirating is a good example here) or make the user any kind of money. This is software for engineering, farming, architecture, programming, etc. costs so much. The development cost isn't actually worth as much as they charge, but if it isn't for personal use it and makes someone else money they want in on that profit. An example is solidworks engineering cad which I used in school. The student version is about $70 while the professional version is which is nearly identical is almost $1,000. They only difference between them is that you have the right to make revenue from using the product with the professional version.

The best one that I can think of off the top of my head is when Napster got sued. I can't remember which record label originally filed the suit, but several companies joined in on the suit and Napster was ordered to pay like $25 million. For those that don't remember, Napster was a P2P file sharing site that users could basically share whatever songs and albums. Since they made no effort to limit or prohibit the copyrighted material and benefited financially from it, they were ordered to pay.