Should 1099-MISC, Box 3 (Other Income) be reported on 1040 Line 21 or Schedule C?

In 2012 I opened a new bank account with a local credit union and was given a promotional bonus of $100 deposited into my account after completing qualifying activity. The income was reported to me using Box 3, “Other Income” of Form 1099-MISC. Normally I would expect to receive a 1099-INT for this type of income. Since this is a 1099-MISC, how should I report this income? Line 21 “Other Income” of Form 1040 along with Schedule C are the two that come to mind. While Line 21 may be the simplest, if I report via Schedule C I have some investment expenses I may be able to claim with the account (i.e. postage, office materials used for account maintenance, etc.)? Since it is under $400 I also would not be subject to SE tax. Is Schedule C the way to go or should I still report via Line 21?
    Line 21 and the investment expenses to Sched A.
      Contribute an answer

      People come to TurboTax AnswerXchange for help and answers—we want to let them know that we're here to listen and share our knowledge. We do that with the style and format of our responses. Here are five guidelines:

      1. Keep it conversational. When answering questions, write like you speak. Imagine you're explaining something to a trusted friend, using simple, everyday language. Avoid jargon and technical terms when possible. When no other word will do, explain technical terms in plain English.
      2. Be clear and state the answer right up front. Ask yourself what specific information the person really needs and then provide it. Stick to the topic and avoid unnecessary details. Break information down into a numbered or bulleted list and highlight the most important details in bold.
      3. Be concise. Aim for no more than two short sentences in a paragraph, and try to keep paragraphs to two lines. A wall of text can look intimidating and many won't read it, so break it up. It's okay to link to other resources for more details, but avoid giving answers that contain little more than a link.
      4. Be a good listener. When people post very general questions, take a second to try to understand what they're really looking for. Then, provide a response that guides them to the best possible outcome.
      5. Be encouraging and positive. Look for ways to eliminate uncertainty by anticipating people's concerns. Make it apparent that we really like helping them achieve positive outcomes.