A friend of mine sent me this link to Jennifer Aikman-Smith of Dragon Dreams' blog where she talks about how badly her business has been affected by people copying her charts. She also discusses how many incidents of copyright violations she has seen. Here is the link so you can read it for yourself.
There is also a link on that blog to something written by a Business attorney that explains why the "fair use" clause of the copyright laws in the US do NOT apply to needlework charts. It explains what fair use actually is and what it is not. Copying a needlework chart does NOT fall under the fair use clause of the copyright laws.