I too do a lot of browsing and looking at quilts and almost all the time I can figure out how it was made. I wouldn't copy a truly original design and say it was my own but, as one person said, a lot of quilts are made up of traditional blocks put together in a different way or use of color.
Something I found interesting is that in EQ6 all of the blocks are not copywrite (unless you install an add-on by a specific designer) and they can be used any way you want to. You could say that it was inspired by a certain design.
I do purchase patterns too.