No, of course not, you don't abandon your idea. You do make sure that you don't use any trademarks of copy or any copyrighted material without permission. But think about it -- where would the western world be right now if nobody ever imitated anybody else's good idea?
It's not unethical and not stealing as long as you respect intellectual property. And you don't have to be the first to be the best. Sometimes being second or third is even better.
Question added to topic Legal Basics For Startups • December 4, 2007
Is it unethical to start a business that is just like another business?
I have an idea for a product based business and have found a similar business online. Some of the product offerings are almost exactly the same as what I'd like to offer with a few exceptions such as the art and wording. I don't want to appear as if I'm copying, or worse stealing some else's work. Do I totally abandon my idea? Help!