IMHO: A startup, while in its MVP stage, should go ahead and do whatever it takes to determine there's a customer demand for whatever product they are making. In Grooveshark's case, they should stream copyrighted works and find out what their customers want and what they're willing to pay for. Once they can determine a viable market, then it's time to get legal. This also will influence their business plan since what their customers may want to pay will not cover the costs of what it takes to produce their product.